- Most major cities have at least one comic shop. Heck, I came across three different comic shops in Cardiff; London has at least eight per my Google findings. When I was in London last week, I finally found Orbital Comics after meaning to for a while; they're really good, especially in stocking more independent stuff and zines. My friend Zach noted just how many there are, and yeah, they really are the place to go if you're looking for the less mainstream kind of thing. Places like Abstract Sprocket in Norwich and Dawn of Time in Lowestoft help to keep up my need for comics locally, and I've found them to be really friendly and helpful. (Especially Dawn of Time: from their vast number of back issues to the coffee and hot chocolate to the people behind the counter who really do befriend you, it's excellent.)
- Forbidden Planet: One of the main retailers, they have stores nationwide in several key cities, including London, Bristol and Cambridge, as well as Cardiff, Edinburgh and Dublin; there's even a branch in New York. FP have two websites, Forbidden Planet and Forbidden Planet International (confusingly, International has the .co.uk domain.) Forbidden Planet are great for action figures, bobbleheads, comics and what have you, and often have an extensive sale section of comics and graphic novels; some more recent volumes may also have a £1 or £2 discount as well. There have been times where I've spent a full hour looking through in their Shaftesbury Avenue location. Sometimes they get exclusive merchandise in as well, so check that out.
- Traveling Man: The other chain comic store I can think of, Traveling Man have a few locations up north in York, Manchester, Leeds and Newcastle; the only one I haven't been to is Leeds, despite being there one summer a few years back! Of note is their 50p back issue boxes, where you'll likely end up with a good pile of comics - I know the time I went to their York branch in 2011 really helped to found my love of comics, coming out with several Captain America issues only a few weeks after I'd seen the film. I made sure to let them know that when I returned last year.
- You cannot beat a good bookshop. I struggle to ask who does not love it. They can be hit and miss sometimes, but you might come across back issues and trade paperbacks in some second hand places.
- Waterstones are pretty much the pinnacle of any bookshop in the UK. They're our Barnes and Noble, basically: a staple of the bookshop community. Without Waterstones, I don't know what I'd do. I still mourn the loss of Borders, I truly do. At this stage, I might as well see a psychiatrist about it. Waterstones are really great with their graphic novel and manga section. They get new volumes practically every week, and in some branches fill up the equivalant of a wall. Although at full price, with cards and everything it can become worth it; still, their selection alone is commendable.
- WH Smith aren't so great, honestly. Their graphic novels - in my experience - are treated as cigarettes for children, teenagers and adults, held behind the counter (or right by the counter), and made really awkward to get to. Most of their stuff is Titan imports of DC/Dark Horse comics, or Panini's reprints of Marvel stories, so there isn't really much to choose from. They're better in the magazine department, with issues of Astonishing Spider-Man, Essential X-Men, Wolverine and Deadpool, Incredible Hulks and Marvel Heroes racking up the newsstand.
- The Works will occasionally pick-up Marvel back-stock, and sell premiere hardcovers and trade paperbacks from four or five years back for bargain prices; this was certainly the case at the start of 2012 and 2013 - I ended up spending a lot of money - but I haven't seen hide nor hair of anything so far this year, so it remains to be seen if they're getting any more stock in.
- Amazon: There's stuff out there about how Amazon are unethical, treat their workers poorly and ... but honestly, it's one of the best places to find graphic novels at the cheapest price. Obviously, there's lots of different sellers on there, but usually Amazon directly are fine. It's maybe not the best place to look for individual issues, but with actual graphic novels it's fine, and I've never had an issue with damaged items. "Related to Items You Viewed" comes in really handy when it comes to graphic novels, just to be able to navigate the back catalogue of graphic novels without having to heap through Wikipedia articles and the like.
- eBay: I'm not all too big on eBay, but for rarer and out-of-print items, it really is the place to go.
- The Book Depository: It has book in the title. 'Nuff said. A lot of bargains are available here.
- Digitial comics: So far as digital comics go, there's both Comixology and the Dark Horse Digital sites/apps for individual issues, and the Marvel Unlimited subscription feature. All of these sites offer a number of free issues as samplers, which is pretty great. Both iBooks and the Android Store have a selection of digital graphic novels available.
- The library: Honestly, this is a haven so far as reading graphic novels cheaply - or rather, for absolutely nothing at all - is concerned. You might prefer to buy volumes to add to your shelf, but loaning is useful for finding your way through new material or content from the past couple of years, especially with volumes which may no longer be in print. Every so often a library will sell off their excess stuff to allow new books to come in, so make sure you look out for those. Each county library should have a website where you can reserve and search for items, for a small charge at most, which makes securing graphic novels really easy. For students there shouldn't be a charge; lucky for teenage readers, right? Requesting books in is easy as well.
- Borrow from a friend. It seems obvious, but to borrow it from a bestie rather than spend £10 or £20 is just logical. Plus, when a friend raves about how awesome the book is, then it's the easiest way of seeing if you agree.
- HMV can be surprisingly great, especially since going in and out of administration in December 2012. Their merchandise section seems to have expanded a lot, and they carry books, mugs, t-shirts, badges and other stuff. Stuff like Star Trek Into Darkness and Days of Future Past can be found in graphic novel form.
- Car boot sales are hit and miss, sure, but if you can get past the fact it involves the backs of peoples' cars, then it's a great place to look for back issues. Last summer I was able to find Jim Lee's X-Men #1 for maybe 40p? I was pretty chuffed about that.
- Charity shops are again hit and miss, but I find places like Oxfam more prone to end up with stuff like back issues and graphic novels, often for reasonable prices of £1-2 an issue (sometimes £3) and trade paperbacks for £3-8, depending on the scarcity of the item.
- Memorabilia shops are often a better place to find this sort of thing. I know in Norwich we have both The Movie Shop and Beatinks, which always carry shelves worth of graphic novels amidst CDs, DVDs, Blu-Rays, books and other items. Honestly, just look through the shabbier side of town, and you're likely to find at least something.