Well, I got the Abus Granit X-Plus 54 (or whatever order those words go in) for £42 off cyclexpress.co.uk and I'm very happy with it. It doesn't weigh that much considering the peace of mind it gives me, and I'm not too bothered about the "what ifs" regarding lock-pickers out there.

Regarding the shackle width, I've really noticed that the width of this lock helps compared to my old Squire U-lock, I can lock my bike round traffic lights now. And the holder it comes with (USH it's called) is pretty good, so there's not much point spending the extra £5 or so for the other holder, unless your bike has no cylindrical tubes (the USH only fits round perfectly cylindrical tubes).