Personally I could care less about the Turbos, the ones I have/had didn't seem to do much other then hang out on the rock work and occasionally clean the glass, I currently only have one turbo left, and switching all my snails to nassarius and cerith.
If your LFS does not sell them you may want to try seeing if they can special order them for you - I know mine will do that for anything I want that they don't currently have in stock.
I can't remember if you have a sand bed, or crushed coral? If a sandbed seriously try to get some of the nassarius snails, I got 5 the other day and its amazing how clean my sand bed is in the areas they have been in, I am going to go get another 6 more of them and 6 cerith next week. Dunno how the shipping is to England, but worst case scenario, I could get you some here, and ship them to you if you wanted - I pick them up for 1.50 each or 6 for 10.
edit* I also have a couple friends in London, don't know what locale you are in, but I could ask some of them if they know of any shops you may not have found, that might carry a wider variety of inverts.