Wife's car, same engine, is doing this too. I've read online about this, on various other forums and the consencous seems to be the pump getting worn. Let me guess it's getting on a bit mileage wise? And it's started doing it only as the weather's got colder?

I've bought a spare pump which I'll fit at some point, in fact this thread might be a catalyst to try it this weekend. They're fairly straightforward to do as long as you've got the bracket at the back so you don't have to set up the piston TDC timing.

Valve clearances should be checked at 100k. If they're loose you need to shuffle the shims around then buy what's missing at £8 per piece. Ours is at 162k and has not been adjusted, however the fact that it starts 1st time (as yours appears to) and does not smoke at all (does yours???) makes me suspect the clearances are "OK".