OK. My allowance was 2 bags. Checked one in at Barcelona and the second one in at Heathrow Terminal 5, absolutely no problems.
Although we had a discussion a few weeks ago about the 'did you pack this yourself?', I did check the bag before accepting it. Terminal 5 is excellent in providing a 'repacking' area!
However I was not asked whether I'd packed it or whether it had been tampered with at either BCN or LHR.