well if the bike you've got can fit 22s and you're not running with mudguards, generally you could fit 25s no problem and not have any fork/frame clearance issues. Even the very narrowest of rims would be fine with a 25.
If you're light then a 23mm will do for almost any occasion but depends on if you want comfort over weight saving? A 25 at a slightly lower pressure might still have a similar rolling resistance as a 23 but offer more comfort and certainly opens up a wider range of choice of tyre.
There's bags of cheap new tyres out there if you look for them. I just got 2 new Michelins for £10 from Chain Reaction but that was the last.
You can get all black Vittoria Zaffiro tyres for £6.60 from Parkers http://www.parker-international.co.uk/1 ... gn=pid1993