I recently got the Ultimate Practice Lock and I'm happy with my purchase. It might not be the best thing out there, but I can go from one single pin to 6 security pins (spool). The tolerances are tighter than lower quality locks so it's a bit more of a challenge. I figure once I master 6 pins with a few random spools I should be able to handle most tumblers.
Then I also got the idea to call all the local locksmiths and see if they were throwing away any locks or had any laying around. Apparently, this is not uncommon. I was kind of nervous, but what's the worst thing that could happen? I called 5 or 6 places and told them "I know this may sound weird but do you have any old locks that you're throwing away. I like to practicing picking them as a hobby." The first few just said no, then one said they throw all theirs away immediately then someone suggested I call a specific place. I called there and the guy knew exactly what was up and told me I could come grab a few and, bonus, return them a few weeks later to get some more. When I got there he wanted to know if I was looking to be a locksmith and looking for a job! He hooked me up with some medium-difficulty locks, and a few expensive locks (BEST) that I have no hope of picking yet.
I'm still hoping to pick them before I return. So call around and maybe you'll get someone who loves locksmithing and understands your passion and would want to help you out.
My wife manages apartments and she has a box full of locks she will never use. The keys are lost but they don't throw stuff away. Other apartments might also, but I'd expect to pay a couple bucks (or quid?) for them.
There's also eBay, which is great for finding more uncommon locks. I got a tubular and some pad locks from there on the cheap.
All in all, I'm happy with the Ultimate Practice Lock until I can fully master it. If you find or think of any other good sources, please share.
