it depends what they want done.
if its just a clean of all woodwork, windows+cills, doors,bathroom,kitchen etc then probably around £80.
if they want extras like oven/hob/extractor or carpets then charge on top.
we do an average all in price ie- general clean +oven/hob/extractor and carpets for around £200 on a 1 bed flat and £250 for 2 bed flat and we are always in great demand from the local agents and landlords.
its a lucrative business to get into just remember they usually want it done in a hurry and to the same high standards every time .