The issue to be careful of is the insurance company attitude to not locking. I dont subscribe to the common moan that they try to find excuses not to pay, but they do expect you to do all you reasonably can to make like difficult for a thief. That may well incluse using locks if they are fitted even if people can hop over the door.
As an example of their attitude, a pal had his car stolen. When recovered there was no sign of forcible entry though there was bad damage. He could only produce one set of keys having told them early on that he had two sets so they took the view that his wife had left the keys in the car. The scrotes themselves took the "no comment" route. No insurance payout. Probably justified - his wife is a bit dippy. Some people mightn take the view that accidentally leaving the keys in the car was an insurable event. They didnt - they took the view that the insured hadnt taken proper care of the car.
So personally I would lock the car up even if it was an ineffectual step.
