Absolutely - if anything, there’s a reluctance to use formal titles in the UK in general.
I used to teach at university - students and staff alike just use first names when addressing each other. When signing emails, we just use our first name, no letters, job title, anything.
It’s even something specifically touched on in our orientation guide for foreign students.
As for newspapers and Prime Ministers specifically, one of the biggest newspapers, The Guardian, has a cartoonist who has always drawn David Cameron with a condom covering his head. There’s absolutely no deference shown to Prime Ministers here.