Guitars and Central Heating

[chillidoggy]

If you're worried, keep your guitars in a Hiscox case, and take them out when you want to play them.

[cacofonix]

Get a radiator humidifier.

It's a ceramic container that hangs off the top of the radiator by a coat hanger thingy.

Not hugely expensive IIRC. Betterware or one of those type of catalogues should have them.