basingstoke, but it's also likely to be relative as to the market rate.
Your factors a and b shouldn't be viewed in isolation, because the over riding element of a job which is (shall we say) unskilled and relatively uninteresting (compared to say, being a vet, since lots of people like animals, or taking care of children, since lots of people love children) is the wage you're getting in return.
and people are unlikely to do it for less than a competitor pays. that's one of the strongest influences here.
lawnimp says that £8ph isn't great. but i wonder what she does for a job, what degree she has, what industry qualifications, and how many years she's been with her employer or in the sector? it's all relative, isn't it?
I think £8ph for an office admin job, which is essentially unskilled, with the potential for wage rises and a relatively flexible part time approach - surely that's a gem of a job for returning mums or folk without any specific skills/ established career path?
A friend of mine is a teacher and works in a London school (lives outside), I'm pretty sure she's not on £33k a year based on her comments wrt buying a house last year, although I'll admit to not knowing for definite.