Congrats on your IR GT.
From Conington you are better off talking to East Mids when airborn if heading West or North West and Luton or Stansted if heading South. I have found Cottesmore can sometimes help but I don't think they have a direct line to London and they are normally closed at weekends. Lakenheath will not always understand what you want.
I faxed the FP to a controller at Cottesmore for info once which helped although in theory you should be able to nominate control units as information addressees in the top bit of the FP.
Never used London Info.
I hope this might be of help.
What is your next move?
Regards