I think it's not relevant enough to bother showing on screen. Who cares what their exact ages are? Also, as long as ages aren't stated, my headcanon that Blackpool is set in the same universe as Broadchurch where DI Peter Carlisle for some reason changed his name to DI Alec Hardy between the two investigations still works :P
A FANDOM User
When Hardy was taken to hospital after collapsing at the hotel, sharp-eyed viewers noticed that on his patient whiteboard was the birthdate October 16, 1969. So Alec Hardy is 18 months older than the actor who plays him.
That means he was 43 during the Broadchurch investigation and 44 during the trial. Supposedly Broadchurch 3 is set 3 years after series 2, so he'll be 47.