I was slightly confused as to why BA decided to launch all of those routes from LHR, as I find it is a waste of slots and all of these routes can operate successfully out of Gatwick, along with their array of leisure routes.
The LHR summer seasonal routes seem to work extremely well for BA. Premium loads are good and they are a better use of off peak departure and arrival slots than an extra off-peak rotation to FRA etc.
Also, one benefit of leisure routes over business routes is they book out much further in advance and there's much clearer visibility as to their performance.