sean
If it is a show room, the chances are they'll want a handover clean, which should be a spotless 'showroom' condition clean. Always remember that the windows are an important part of these cleans as they really show off your work! What to charge depends on what you want to earn!£100/£150 a day is not unreasonable so maybe try that, keep it on the low side to get started, do a bloody good and THOROUGH job, and take it from there. sometimes you win sometimes you lose, thats how you get a feel for pricing, good luck mate!!!