In very bad weather, as a Heathrow Director, I've vectored aircraft as far south as almost the south coast... as far north as Luton, as far west as almost Swindon and as far east as Southend - all following co-ordination with the TMA people, for whom I have absolute respect.
I merely wished to clarify the term "Heathrow ATC". In my book it's not just the people at the airport.