It's crystal ball time.
* Will the property be occupied when the work is in progress
* Are any floors sealed down with tiles, laminate etc
* How many final circuits will you need (lights grd, lights 1st, ring grd, ring 1st, ring kitchen, immersion heater, boiler, loft, shed, garage etc)
* Standard white switches and sockets or metal ones
As a totally open cost, in London for a open job (free access and no need to give service for people living in each day) £6k.
That will extend upwards if routes and service reinstatement required each working day.
I'd suggest you map out your house and work out what you feel you need.
Socket volume in each room, type of lights in each room, switches, double switches (upstairs / downstairs hall lights) etc
Add in TV cables, BT points and data cabling for PC's plus alarms if you intend to have one.
The NICEIC are not the only approved body for Part P electricians and the best place to look is
http://www.competentperson.co.uk/
BREC-ECA
BRE Certification Limited and the Electrical Contractors' Association
0870 609 6093
BSI
British Standards Institution
01442 278577
ELECSA
Elecsa Limited
0845 634 9043
NAPIT
Napit Registration Ltd.
0870 4441392 or 01623 811483
NICEIC
NICEIC Group Ltd
0870 013 0382
