I've never done a positioning flight (in order to fly cheaper in a premium cabin) but I've been doing some research and I've got a question perhaps some helpful FT board members can answer.

Lets say I want to fly London - Hong Kong in Club but the flights are £3,000 + on BA. However, if I was to fly from Stockholm/CPH/OSL etc.. the price is only £1,500. The flight would be via LHR.
e.g. CPH-LHR (BA) 20 hour transfer in LHR. Then LHR-HKG.

I understand in order to achieve this I need to buy a flight or redeem Avios to get to CPH.

However, as a London resident rather than spend 20 hours in LHR am I free to go home for the night? And secondly can I check in my luggage for the long haul flight when I return after the 20 hour layover. Or can I only give BA my hold luggage at the beginning of my ticketed travel?

Apologies for a basic question but we were all inexperienced flyers at some point. Let me know if I need to clarify any of the information or if I've got muddled and incoherent.