As I know from experience, OP is talking about Terminal 4 (the post only says "LHR").
The T4 smoking area was indeed a very pleasant surprise, but I was wondering if any other terminals (particularly T5) have followed suit?
I've got a (tight) connection from T4 to T5 coming up and I'm considering between clearing customs to have a cig landside, asking the staff nicely to allow me into T4 for a cig (but this means clearing security twice - in both T4 and T5) or just proceeding to T5 and trying to survive.