In reply to Tru:
I really rate DMM Peenuts especially for limestone. It's usefully to have some smaller nuts. I've done plenty of climbs where they are the only things that go in.
I notice a lot of people don't bother with the larger cam sizes (DMM 5 and 6) but I have both and use them all the time, the 6 especially will go in where nothing else will and you know it is never going to slip out.
Second what other people say about more 120 slings and making up sling-draws.
I'd also get a 230 and a 480 sling, these are useful in the Peak for chucking round boulders at the top of routes for easy peasy anchors. Yes you can use your rope around a boulder but I've found in practice this causes your rope to wear out quicker.
Also plenty of screw gates, particularly if you are climbing somewhere like Pembroke and are setting up anchors for abseiling.