I had a similar problem loosing fuel used information somewhere between alderney and the solent via brixham which was a real pain!
I've never recreated this problem, although i did report it to Barrus technical who claimed never to have heard of this before. I was quite frightened when i founf out i only had 10li left when i got back up the itchen
I will try what you are saying gavin and report back.
My only thoughts at the time were the engine had been running for over 5 (maybe more) hours solid which i am not sure i had ever done before. I don't think i have since either.