Hi Julia, and welcome to the site.
Your sums don't add up!! No Wonder
The average price for an apartment builders clean will be around the £145 mark....depending how large or small it is, of course. It will be up to you how much the sparkle clean is, however, we have found recently that after all our hard work doing a spot on builders clean, the trades men trash the place and slap paint everywhere....and a sparkle clean can take as long as the builders clean.....so don't under price your sparkles.
Larger houses though.....whatever you can get away with!! 2 / 3 bed houses could be anything from £150 - £200 for the builders clean....we even have some 4 / 5 bedroom houses that we have done for £330+ for the builders clean....and the sparkle clean on top of that.
The areas that will take the time are the Kitchens, bathrooms / ensuites and the windows. The more bedrooms that it has makes no difference really, as they are an empty room and you have only switches, skirting, radiators and doors to clean as a rule.
Other than getting used to working around other trades people making a mess in rooms you have just cleaned......then i wish you all the best
Kind Regards
Tim