Keep gutters clear
Blocked gutters are behind a surprising number of damp problems. When leaves and debris stop water draining, it backs up and spills down the walls instead. Clearing them once or twice a year, especially before autumn and winter, is one of the simplest and most effective things you can do.
Check after high winds
After a spell of strong wind, it is worth a quick look at your roof from the ground, or with binoculars, for any tiles that have slipped or gone missing. Catching this early stops water getting into the layers beneath.
Watch for moss and growth
A damp climate encourages moss, which holds water against the tiles and can work its way under them. A bit of moss is normal; heavy growth is worth keeping an eye on and, where needed, having dealt with properly rather than blasted off, which can do more harm than good.
Do not ignore the small stuff
A single cracked tile or a bit of loose flashing seems minor, and it is, until the first heavy downpour finds it. The cheapest roof repair is almost always the one done before the water gets in. If you spot something, it is worth a call.
Have it looked at if in doubt
If you are unsure whether something is a problem, ask. A local roofer who knows the area and the weather here can usually tell you quickly whether it needs action or can safely be left, and give you honest advice either way.