Thanks very much for your replies.
The information about 46 Squadron looks very interesting and I will certainly have a Google, although just on a quick look I'm not sure that the subsequent locations match up with the service record. This was partly why I was wondering if he would stick with the same squadron or go where he was needed in his role as Accounts Clerk.
He was William Frederick Hazle when he served in the RAF, born in 1901. The rest of Grandad's life details I'm pretty well up on, thanks to my Dad - it's just this mysterious reference to HQ 4 Base Area in 1940 that is intriguing me, as I wondered if that might finally confirm the story that he was in Norway.
Thanks very much you for your help and pointers - I can see many interesting hours ahead!