So after a week or so of me loosing it everytime the cooker tripped the switch, my OH finally went to remove the old breaker and put a new one in - on taking out the old one he finds that one of the two wires that go into the breaker is not joined properly to the breaker - it was not screwed in. So he screwed it in and there you go - all fixed.

Another quality job done

If, as you say, the house was rewired recently. Then it would probably be a good thing to check all the other breaker connections. With a loose wire, like the one you had, you can get some overheating. Just make sure the main breaker's off first.