Right, just spoken to FC and all is sorted. I explained the problem, ie. that I'd booked the tickets on Sat and, whilst I can access the booking by entering everything from scratch, should it not pick up the booking automatically if I am already logged on? She checked and said that the person who had booked it had used a "dummy code" used to signify that the fare is not eligible for mile earning. I said that I had definitely paid for S class PE and upgraded to UC which she soon verified and said "let me pop those FC numbers back into your booking". I confirmed that they were the same numbers used to provide the miles for the upgrade but she asked me to give them again as she was on a different screen and couldn't locate them easily. So I read them out and thanked for all her help and...now...finally, success! When I log on to FC and click on Update Booking up pops my booking!
Thanks Paul for putting me on the right trail - just as well otherwise I bet we'd have ended up having problems later on!
Finally, she also said that on return from our trip I will need to contact them to manually get our miles & tier points added to our accounts, "because it's an upgrade". I recall we had to do this a couple of years back when we had paid for Y and upgraded to PE.
