I am in the same position, Mark, and have owned my 993 for almost 3 years. We had a garage conversion done a couple of years ago, so I either kept the 993 on the drive or sold her and got something else. The latter choice was not an option! I drive a short distance (6-8 miles - enough to get the thermostat to cut in) each way to work, and she sits in a company car park all day. At the weekend I always try to give her a good run, and I plug in a Ctek battery conditioner every month or so to keep the battery in good condition.
Don't let the fact that you don't have a garage put you off owning a 993. They do not attract as much attention as a Ferrari or Lambo, so most people will not take any notice of it on the drive and she should remain secure (or as secure as any car, depending on your neighbourhood!).
If you give her a good wax a couple of times a year, this should protect the paintwork from UV and bird cr*p for the most part. I find that bird cr*p is the biggest issue in the summer, so make sure you get this stuff off ASAP. Don't wipe it - soak some kitchen roll in water and apply to the "deposit" until it is soft enough to simply slip off with a hose. The other thing I noticed last year was wasp poo! Yes, you heard right! There were little marks appearing all over the roof, and when I found a wasps nest nearby, the guy that came to get rid of it says this was what the marks were on my car! Get this stuff off quick because it burns into the paint.
These cars are extrememly well engineered, in fact in most cases they are over engineered, so will withstand many years of the UK weather, providing you look after the paint as described.
With regards to driving them every day, I have not had a single break down in the 3 years I have owned her, and I strongly believe this is because I drive her every day. Get something with a few miles on, and that way you won't have to worry about putting a few more miles on and losing money. You can concentrate on the fun part which is actually driving the thing!
Good luck in your search, and keep us informed.
Darren