Where are you staying?

The biggest single problem is it might take you 30 mins to get from your hotel back to the airport to then get on a train anywhere.

Years ago, the Crowne Plaza used to have a decent restaurant in house so getting your friend to meet you there may have worked (but I don't know what the place is like now...)

You could probably find a blinding curry in Southall but that'll be more about the 'experience' than being haute cuisine....