This a "new build", so I was wondering if it is:
a) a new house being built by an NHBC builder, which I suspect it's not as the OP wouldn't be getting the electrical works done by someone else?
b) a new house being built to the design or requirements of the owner, possibly a "kit" home being erected by a building company who are not NHBC registered? If this is the case, I would have thought there must be an architect involved, in order for a Certificate to be issued in place of the (useless) NHBC certificate, otherwise, without either of those (other versions are available) there would be difficulty on a resale within 10 years at least. So, assumng an architect is involved, I would have thought the best route is to get him/her to select the electrical contractor as he/she will have experience of working with some firms and know which ones will do the job correctly, and will get everything through Building Control. That way, the owners have a comeback if anything is amiss.
It may be tempting to use a cheaper option for the electrics, but I feel it is wiser to pay the right money for a safe job, and maybe spend a bit less on the shiny bits in the kitchen, bathrooms etc. Huge value when finished, a few hundred extra on electrics is a better route. Folks seem always to skimp on the unseen bits, the services, electrics and plumbing, yet these are the very heart and veins that power the dream home...