Yes, they get the flat at Downing Street. It's rent free
The PM is taxed on the accommodation as a benefit in kind.
Boris has given up a lucrative job writing for the Daily Telegraph, and appearance fees on TV programmes he used to do.
I think the PMs salary shouldn't be so high that people are attracted to the position for the salary, but it should recognise the responsibility the role carries. £150k isn't all that much relative to what our captains of industry earn, nor to GPs and other medical people, head teachers, vets, lawyers and many other jobs.
It's only just over 3x my salary and I don't hold a particularly exciting or responsible job.