BOS-LHR-DXB with a London visit
Suppose the first question should be do you have permission to enter the UK ?
If yes everything else you suggest should be fine.
If you wanted you could check in your carry on when you got as far as LHR or else I'm fairly certain that LHR has left luggage companies that will hold it for a charge.
What time does the earlier BOS flight get into LHR ? If am I'd head to the arrivals lounge to shower and freshen up before heading into the city.
cs