Thanks, Graham, and for the useful link (with an intriguing reminder of voices from the past). Lots of good stuff.
Funny how one's attitudes change (and probably just as well, otherwise we'd all be opinionated bores). Until recently I would never even have considered an electric pump. However I read a DCA article by an intrepid cruising dinghy sailor, and subsequently e-corresponded with him, who has a Rule in his cruising Mirror (his boat has gaff rig complete with a dinky little topsail!). He briefed me on batteries etc. I usually sail alone, and the thought of flicking a switch and leaving the pump to get on with it is appealing (as I get less young?). Conversely, waggling the handle of a diaphragm pump while trying to get on with sailing, in what might well be tricky conditions, is one more multi-task. On my Storm Petrel (which was prone to shipping water), the manual pump handle was convenient to the normal helming position. In my present boat, that's not v practicable. Mind you, judging by Cavatina's dry-ness and stability in a considerable seaway off Kippford, in September, I don't think pumping large amounts is likely to be a frequent need, perhaps in contest to a Mirror (absolutely no disparagement intended). Anyway, that's my train of thought. Perhaps I should wait and see how I get on. One thing I have done is to fit a drainage bung in the transom, so emptying the boat ashore is now not a chore.
While assembling information, I shall have to admit my ignorance in another field by asking for advice about electric circuitry on a boat. Do all connectors, switches etc have to be waterproof? If not, what can one get away with? If they do, where's best to buy them? - e.g. Maplins? I looked at a few of the on-line chandleries, and I'd be forking out more than the cost of the pump + battery for the wherewithal to have a simple waterproof circuit!
Michael