Mouses.

[Dog Pants]

After all this investigation I've come up with a little checklist for choosing the right mouse, since when I started I didn't know where to start. What do you chaps think?

Play a game for a little while.
Stop and look at how you're holding your mouse:- Finger and thumb or palm?
Look at which parts of your hand manipulate the mouse, is your hand or wrist resting on the mat?
Where are your fingers on the buttons?
Where is your thumb relative to the buttons?
How many buttons do you want (more is not necessarily better)?
How heavy do you want it?*
Look at some mice, reduce to ones which look to fit your hand (shape, button positioning).
Get rid of the bloody ugly ones.
Reduce according to budget.
Go try out the survivors.
...
Profit!

*I haven't worked out how to decide on how heavy you like something other than by getting hands on. Similarly, DPI doesn't really seem to make a huge difference to me, I just adapt to whatever it is.

[Dog Pants]

Well PC World had the Imperator, RAT 5 and 7, and G500 out of the options I wanted. Unfortunately the guy who came over to offer help couldn't get any out of the box for me to play with, so I might as well have ordered it from Amazon in the end, although all the boxes had windows so I could see the size of them (the Imperator was a little small). So out of the ones available I went for the RAT 5, since I could fiddle with it and get it to fit even if it wasn't perfectly comfortable. Playing with it a little bit now I'm happy with it, the buttons are in good places and I've found a nice weight (I'm surprised at how much difference I noticed there). The salesman made a vague attempt to sell me the RAT 7, which he said he had, and under the impression I didn't really know what I was doing ("Gamers use these mice for M-M-O-R-P-Gs"), but since the only difference is the resolution I convinced him in the end that he'd spent £30 more than he had to and he admitted he'd have been better off with the RAT 5. A lot of the decision was also based on the fact that despite appearances Mrs Pants thought the RAT was the best option for her gammy claws.

EDIT: I was spotted writing this. I must retract my statement about Mrs Pants's mutant appendages. She has lovely hands.

[FatherJack]

A shame your PC World isn't like the one by me, in that they have most of the mice you list out of the boxes in an aisle-long display that you can touch all you want - which also serves to demostrate which ones/parts are easily broken. It is a pretty big one though, being the result of a merger between what were two already pretty large PC World and Currys stores next to each other.

Still, it seems to have worked out in the end.