Frozen Central Locking

2006 TD5 with Central Locking. Had first really cold morning on Merseyside today, tried to open doors with remote. Door would unlock them immediately lock again, tried with key only as well. I had to go round and unfreeze the 3 doors locks before they would stay open. Any hints or tips on stopping this happening ?
Thanks John

I give mine a good soaking in spray oil every now and again. It seems to keep the moisture out and help a little.

Thanks I will give it a try, was there for nearly 15 minutes this morning. Neighbours in their normal cars found it amusing, go anywhere Defender, well if you can get in it !