That sounds promising but when I spoke to building control they said that it's not their job to do a Part P
Haha, next they'll be saying they dont want anything to do with partA, partB, etc: Part P is no different from the other parts of the building regs!!!
But just incase theres been some confusion, most domestic electrics are notifiable to them, but a domestic installer can self certify their own work as building regs compliant (thus no need to involve BC), if you are not a domestic installer you have to notify the old fashioned way (which has obviously happened in your case as you have had him down to inspect other stuff)... There is no requirement to be a DI to do electricial work
Anyhow as to whether they should be able to pass an installation without an electical certificate as defined in BS7671 is a matter of much discussion, clearly the lack of one means the install is not to BS7671 (as it requires the cert be issued!), but that inself need not be barrier, BS7671 is not a legal requirement, merely just a good idea. The problem is that if it complies to BS7671, mr building control merely has satisfy himself that it does meet that standard as he is told he does, and all is well, if its not to BS7671, he doesn't quite know what do do, he probably doesn't know how to test and inspect it himself and interpret the results!
So where does that leave you? well you somehow need to satisfy the BCO that its safe, the recommended way of going this is to get an electrician to carry out a PIR (periodic inspection report), there is no way you can get an EIC as the new electrician cant sign for design, construction and inspection+testing, and while he could sign for the third on the full form, its going to be incomplete without the signature of the designer and installer!
Hope this explains the process a little clearer