Self Locking P38

In that recent cold spell my P38 suddenly started operating the central locking all on its own. Bit of a nuisance the first time when I had let the thing warm up with the engine running and all the heaters/blowers going and I was outside scraping the ice off the windows.
It also had three quarters of a tank of diesel so leaving it to run out of fuel wasn't an option so I had to rummage through the kitchen drawer to find the old key fob which hasn't worked properly since it got dropped in the dog's water bowl 2 years ago - but that's a different story!
Got in OK, but after then it's carried on doing it fairly regularly. Not every time, mind you, and not always after the same interval. Sometimes it's seconds after driving away, once it was 100 miles up the road. And it's not just in cold weather, it's still doing it now the snow's gone away (I know we've only risen to 10-11 degrees so it's hardly a heatwave but still!)
Can anyone shed any light on this please?

Probably one of the door lock mechanisms on the way out - usually one of the fronts. Only thing to do is to have a look at each in turn and give them a squirt of lube and work them manually with the door trims off. The next thing is to get it plugged in to a Testbook or similar which will 'examine' each lock in turn and report any fault. It's less time consuming but could cost you £40.