Would Swanwick have the capacity to add Oceanic, MACC, ScACC and the extra military stations? Doubt it - so building work would have to be done...
An internal redesign would be needed but yes, Swanwick does have the room. Car parking however would be an issue.
I don't know whether the technology at Prestwick is the same as at Swanwick? I know that touch screens are used at both but the stations look quite different.
Swanwick AC uses a completely different system all together so civil control could not be conducted from Prestwick for London Area sectors.
I would not be at all surprised if this rumour is being discussed at some level and is something to have in the back pocket further down the line should it be needed. I'd say it would certainly depend on what instructions come out of Europe and the plan to reduce the number of European centres to just 5.....