CDRs

After much searching, I have found a stall in the middle of Leicester Market that sells extremely cheap CDRs and all manner of other computer accessories.  It's quite likely that there's a similar stall in most city centre markets

If you prefer to go to regular shop, the best ones to go to are Maplin (go to www.maplin.co.uk to find your cheapest store), Makro or even Tesco actually do quite cheap CDRs if you're still stuck.

Ordering off the internet can prove a little expensive as you undoubtedly incur postage prices, which for heavy items like CDRs is gonna cost quite a bit.
 

Plastic Wallets

Again the good old market stall is nice and cheap for this kind of stuff.  The other option is EBay.  Click here for a nice reputable person who sells them dirt cheap.  They're pretty flimsy, but they do the job.

Paper

Tesco.  Get Tesco Value paper.  It's great!

If there's anything else relevant that you would like to know how to get cheap, contact me and I'll do my best to find out.