Wow! Thanks for all the replies.
The words "fragile", "unreliable" and "death rattle" appear with a worrying frequency. In the short term I am going to think about whether a set of winter tyres (suggested by Steve84N) is the most sensible, and certainly the cheapest, option. It is true that we're unlikely to get 3 foot snowdrifts in West Sussex.
I shall also think about other options (e.g. Fiesta ST as suggested by Monkeydonkeyratmagic). don't hold your breath though - I'll probably still be thinking about this next autumn. Let's hope that Mrs R doesn't get involved - she's the one who a few years ago bought a new Ford Puma never having driven one or even seen one in the metal until she collected it! It was a great little car though.
Anyway, thanks again for all your thoughts and advice. If I ever make a decision I'll let you know.