"I love playing Louisa and it's brilliant being in Cornwall but it's great to have the opportunity to play a different role. When I'm playing Louisa, I spend most of my time trying to educate Martin into how he can be a little more approachable, so it's nice to have the tables turned and play the tricky, difficult one."
Given that home is London, it's fair to say Catz knows the country's rail links well, and her kids do too.
"Obviously I get back as soon as I can every weekend, but they've come up to Leeds and they spend a lot of time in Cornwall."
It's not been confirmed whether Doc Martin, which is filmed every two years, will return for a seventh series.
"It was brilliant to do series six because we didn't think we would," says the actress, who admits she's due some time out after a manic year. "I'm tired and ready for a rest," says Catz.
She can also indulge her guilty pleasure – Twitter browsing, saying "I've got a Twitter persona but not as me. I just like following people I'm interested in."
