OP
Kate
it depends what your going to do with it tbh. Most new 18v sds drills are as good as the older range of 24v drills and suitable for fixings and small to med holes. If you want to do heavey duty stuff then a 28-36v would be a good idea.
for the daddy you could get a hilti 36v monster for around £1200 which is better than any small corded drill. If you cant justify the cost of that then you can get the bosch 36v with two 2.6ah batts for £439, which is a bargin tbh.
Bosch GBH 36 VF-LI (2 x 2.6 Ah, QCC, case) Li-ion SDS+ hammer with quick change chuck
I just got this with the three function, and three batteries, cost me £570. Best decision ever