we’ve got one drawing up a Dorma loft conversion/ground floor extension/interior changes to our bungalow at the moment.
cost for their fees alone was £1750.
However we’ve also getting them to handle planning (need certificate of lawfulness) building regs (inc inspections – using an agency, rather than LA inspector) and dealing with Thames water (we’re building over a sewer) so all fees together will be about £4k.
We had cheaper quotes (had a quote for £800 just to do the drawings) but these guys come recommended by a mate, who has just finished using them, and we’ve seen some of their other work – and liked it.