Hi guys,   I've just had  plans drawn for a 6x6m rear extension.    Im in the process of working out my budget.   Friends and family are going to do all the work.  Except ground works. So I'll need a builder for that.   Anyone have an idea of what I should expect to pay, for 1m deep foundations, damp course, semi engineering brick layer, hardcore, damp proof membrane, insulated concrete base and screed. (Basically everything below the brick work)