I'm not British, but the original Office was done the same way, six eps per season (which they seem to call a series over there?)
It might just be comedies, though. Dr. Who is sure way more eps than that a year.
In America it's generally 22-26 eps a year, with the main exceptions being cable dramas (The Wire, Mad Men, Breaking Bad, Sons of Anarchy, all those types of shows run around 13/year.)