Originally Posted by Bukhara
You can't combine the two bookings into one. The only way around it would be whether you can re-route your domestic ticket and pay change fees etc. In the end, this would not be an economically prudent measure.
You can link your PNR's, although it's not really necessary if the same passenger(s) are on both bookings. If you make check-in aware you have an onward connection, they'll check you in for that flight without a problem so long as you don't undercut any connection times.
I thought that's what I would have to do in the end. Would it make any difference if the check-in is done on-line (in which case I'd check-in for each flight separately) or at the airport?
Also, since the flights are not on the same ticket, would I have any problem upon my return using the lounge in london (arrived from a CE flight, connecting to a domestic cheap one) according to article 7. of the lounge rules, as mentioned in the BA sticky guide?