No problem with a 70 minute connection, minimum connecting time is 45 minutes which is enough connecting from OSL to LHR or vice versa.

The CPH-LHR flights are normally quite full, at least all the flights I've been on have had a cabin load around 80% or above.

Very unlikely with any upgrades, especially as like 50% of the passengers onboard are EBG or *G, so even if they happen to need somebody to op-up the competition will be fierce.