Thanks to Nemesis and everyone else who posted a reply, both to this thread and the "Chann 1-5 help" thread which was also very useful. Looks like I'm going to have to stock up on chocolate biscuits and hope for a friendly engineer who will fit a splitter for me.
The 'guy' that fitted the original analogue box had a sloped forehead and ground level knuckles so it may be that after the install I won't have my longed for splitter, so..... can you get the necessaries from the local B&Q and is it a doddle fitting one?
Alanmelon suggested getting a second box. Well call me Mr. Tightwad but 98% of my tv viewing is on the terrestrial channels, 1.99% of the remaining is Simpsons on Sky
so the idea of forking out the extra dosh doesn't appeal.