Hi, could be a number of things - deep cleans mean different things to different people.
As a guideline it would probably include carpet cleaning, a toilet de-scale and wall/partition washdown, a kitchen deep clean (again what this would entail needs clarification) a high level clean - possibly including light fittings, and a wipe down of all gloss-work and walls.
You really need to agree exactly what is required with your client and confirm it in writing - this could avoid problems later.
As far as pricing is concerned you need to consider when the work is to be done (weekend or overnight work attracts premium rates) but for normal hours somewhere between £20 and £25 per man hour should be acceptable.
I hope this helps.
Musicman
PS. Don't forget your COSHH paperwork, risk assessments and method statements - just in case!