Incidentally, I already use a feed off the (now broken) aerial for the
digital TV card in my PC, and that seemed to work perfectly OK. Does
that mean a standard aerial should be OK? As in, is digital TV reception
"all or nothing"??

Nah. It's not all or nothing. The bit rate gets worse and you start getting
drop out, particularly in bad weather. If you're going to pay for someone to
be up there, you might as well fit something decent rather than a crappy
contract aerial.

Christian.