LHR-CPH/CPH-LHR flights are reasonably full most of the time, but upgrades on that sector are not likely (at least not in my experience as of late).

As said above, 70 minutes connecting time is plenty for connecting at CPH. Even for LHR-CPH, as long as my flight left LHR in a somewhat timely manner, I've done such connections without too much hassle even when my flight left LHR 30 minutes late.

CPH-LHR has SAS and BA flights and there are a few other CPH-London flights (other airports). The issue is that after 7.45 or 8.05 p.m. there are no flights left on that route.