Thanks for your interesting replies, people.
Here, about 30km from Glasgow, power cuts are very rare, spikes are almost unheard of. Maybe we could get a cut that lasts about about an hour every year, and little cutouts less than a second every few months (especially during thunderstorms). The washing machine downstairs also likes to blow the MCBs and cut off power occassionally, bah. The mains voltage stays at around 237-248 V.
I have a UPS. So far its only saved my computers from crashing on the little drops about 4 times in 2 years, but I'm happy with it. Didn't really need it, but its a sort of geek thing. ;-) Before that I had one of the dedicated surge protectors, which now protects my family's PC against non-existent surges. Oh well... ;-)