Howdy Gnat, thanks for signing up! This is my old gym buddy everybody!
Well the reason that you likely haven't lost much mass is that maintenance is much easier than putting on muscle. In other words you possibly will be able to maintain your muscle mass but you'll have a harder time putting more on which may mean that you're not getting the best results from your workouts - which you deserve to as you tend to beast your workouts.
So what I'd recommend unless you're happy at your current shape is to just eat more protein such as eggs. You don't have to have them raw, some people say that doesn't work anyway, but just eat a couple a day. This is possibly a leaner source than most shakes anyway. Eat more tuna too. LOTS more tuna.
Alternatively you could just find a cheaper protein shake. Here's one source: http://www.discount-supplements.co.uk/
Another is a site Janik's raving about, they're even cheaper and focussed on being the 'just the basics' of protein. I'll post here when I've next spoken to him (or you could Facebook him). Alternatively go to Asda and get some Whey Supreme or a health store and get some Body Fortress - they're shitty but better than nothign.
To answer the question of how well they work, they certainly do make quite a drastic difference. My friends on protein shake are all much more massive than those who aren't and the biggest I ever was one in Leeds when I was taking two lots of the EAS 100% Whey. I got massive then and I probably trained harder since! So yeah they do work, but they are expensive, so you've just got to find a way around it! If you're happy at you're current weight and you're not losing any mass however then I guess don't worry about it. Although they are also delicious.
See, how helpful was that?? Tell your friends! And post more!
Btw are you getting an e-mail when I reply to your thread? I want that to be automatic!