Make sure all the sparks quote the same.
A wise move would be for you to consider exactly (well with your planing head on) what you want.
A simple room by room schedule or even a paint drawing showing:-
Sockets per room (consider TV, Sky, Hifi areas, bed location for side tables, hall area etc)
Lights, switches, double switching such as bed and wall- importantly a single pendant is 'X', a group of spots 'Y' on costing.
Boiler
Hotwater
kitchen and appliances, cooker as a separate circuit.
Then consider the fittings, MK are one prices and contract carp is another, same with metal faced items x 3 the MK costs (ish).
You should also agree the rules regarding making good, plaster damage, tile issues in kitchen, sealed floor problems. Repair of such by a builder, plasterer or decorator eases my cost.
BTW £1700 is not OTT, but as others have said unseen- so price means nothing.
By doing so, you will get apples for apples quotes.