gentle warmth will be OK, but severe heat may provoke a variety of paint flaws.
Word of warning; you may be intending to use a mixture of paint types, e.g. acrylic and cellulose based paints. This can easily go horribly wrong on you, and even if you 'buy everything in halfords so it should be OK'.
IRRC (and do double check this to be sure) it is (say) normally OK to use acrylic over cellulose base coats but not the other way around. Annoyingly the paint incompatibility may manifest itself only after hours days or weeks, as a cracking in the painted area.
Even with some kowledge and experience I can still get caught out; they don't always say what type of paint it is on the can, so when (after two different primer layers) you rub down and need to repair a primer area, the feathering in may result in cellulose over acrylic, and consequent problems.
cheers