<<but ATC was very accomodating (It was 11pm) and as soon as we acknowleged we had handling we were cleared for the approach.>>
Just as long as everyone is fully aware that ATC has nothing to do with these decisions. If an aircraft requests to divert to Heathrow the Airport Authority is informed and they decide whether to accept the flight. They can refuse right up to the last minute and I have seen a/c instructed to go-around because the Airport Authority would not accept it. Needless to say, this does not apply in cases of emergency. Usually ATC will handle the flight as a straightforward inbound until such times as the AA refuses it. For diversions by operators regularly using Heathrow all this is handled by the operator and ATC is not involved at all.
As always.... since I retired maybe things have changed..