Hi stinny, It will depend on a few variables ie is existing wiring in conduit down walls, or does it need chasing in or would they accept surface mini trunking? how easy is it to lift floorboards/sheeting?
Where is consumer unit positioned? so no easy answer, best thing would be to decide on standard required & get 2 or 3 quotations from local firms, BTW if any one quotes without looking GO ELSEWHERE!!! because they are pricing on 'worst-case' so will be expensive!
Geographics will come into it also as prices seem to vary around the country, material costs around Â£800 + man & mate/trainee @ around 50/hr, approx 10 days work ie 80 hrs, = Â£4800 as very rough guide in this area, regards SPARX