We are in the SE London / North Kent area and are looking for quotes for a single story 3 x 6m flat roof extension; block walls, render, heavy pebbledash, painting. We are getting verbal quotes of around 1,500 plus vat per square meter to 'build the box' and wonder if this is about where we should be . . . . too cheap = problems, but we of course do not want to pay over. Would this cost include the knock through and all steels, (we need 2 at a T shape) and internal / external decs, and should the dreaded vat included in this merer rate, or on top ? We are not looking for the cheapest quote, we just want to know a fair market rate to help us select the best builder. The internet suggests 1,200 - 1,500 per meter square, but out of date posts . . .(2010-11). As building regs have changed for insulation, flat roofs, etc, I would expect build costs to have risen ? We also have an existing 3 x3 meter single story flat roof extension to demolish first - How much and how long for this ? Any help appreciated and thanks in advance.