Erbauer Double-Ended Impact Screwdriver Bits Set 5 Pieces .
I have a few cordless drills/screwdrivers, but always seems to be short on the bits for them. Personally I like these larger double sided bits , as I find the small sets annoying, and usually end up tipping them everywhere.
These ones seem to have decent reviews and at £4.99 for a set I think they are worth trying.
Just picked mine up and they come in a handy little plastic storage box.