Quick update.
The Erbauer went back to Screwfix, full refund, no questions. Top marks to them.
The 18V PPProPileofPants went back to B&Q, it's main problems being a speed controller which doesn't, and batteries whose capacity is so small as to be of little use to man or beast.
The Axminster White 24V also went back, because it was so poorly made that the mere thought of handling it offended me. It made the PPPoo look pretty good.
Came very close to ordering the 18V Makita at £250, then had a flash of inspiration - most of my power tools are Bosch (green range). I'm very happy with these tools, and use them frequently with no problems. So I looked, and sure enough, Bosch do a couple of nice combis.
I've bought the PSB18, which seems like a very nice drill. £130 from B&Q. Strangely, they also had the PSB24 (24V) at £95 (!!), but it only came with one battery.