After that I don't remember seeing him on TV again for a decade until he turned up as Jack Harkness. Then he's never been off the screen since.
As his Wikipedia page points out, he certainly kept himself busy in between. As mentioned, he was appearing in the West End during the first series of Live and Kicking, I remember he was doing Hair. He also did The Movie Game for a couple of years as well.
I'm also reminded from it that he appeared in an American drama called Central Park West (I remember that was on Sky One and the Radio Times pointed out he was in it) which was supposed to be a long runner but got axed after a single season. And there was plenty more stage work as well, it says here he was nominated for an Olivier Award in this era as well.
It's true that he became much more prominent again after he appeared on Doctor Who, but actors do say that a load of work comes in bunches, because if casting directors don't see you, they forget all about you, and then when you get one job you're on their radar again. I do like him, I know he's an acquired taste and I wasn't crazy about him on Live and Kicking but he's clearly a lovely bloke.