Gatiss also said that the characters in Sherlock have “the same age of the actors, given or taken a few years”. So:

* Benedict Cumberbatch was born in 1976, so he was 34 in 2010 and is 36 now, but I agree with sherli-holmes: he appears to be on the “taken some years” side of the range, so I’d think that he is no older than 35 at present, and was about 33 when he and John first met.

* Martin Freeman was born in 1971, so he was 39 in 2010 and is 41 now: same as before, he appears to be on the “taken some years” side of the range, but obviously a little older than Sherlock, so I’d bet he is about 38-39 now, and was about 36-37 in ASiP.

* Mark Gatiss was born in 1966, so he is exactly ten years older than Cumberbatch, but we know that both canonical and modern Mycroft are only 7 years older than Sherlock, so considering what I’ve written above, I’d say that he was probably 40 in ASiB and is now 42.