Does this mean the electrician could provide a certificate for testing (providing it passed) and I could accept responsibility for the design and construction?
Do you genuinely think you would be qualified to sign this:
I being the person responsible for the Design of the electrical installation (as indicated by my signature below), particulars of which are described above, having exercised reasonable skill and care when carrying out the Design, hereby CERTIFY that the said work for which I have been responsible is to the best of my knowledge and belief in accordance with BS 7671:2008, amended to 2011 except for the departures, if any, detailed as follows.
and a similar one for construction?
Do you genuinely think that your Building Control department would accept that you were qualified to sign them?
I don't genuinely think anything, which is why I am asking for advice not a patronising lecture.
Am just trying to understand if there is anything I can do to keep costs down or do I have to get an electrician to do every aspect of the job?
You need to find an electrician and discuss and agree with
him how much of the work
he is happy for you to do.
Does anyone know if this is correct or if there is an option to split the current wiring without carrying out a full rewire on each?
It's wrong.
And I would suggest that the lack of knowledge it betokens about what the Wiring Regulations require of electrical installations make it unlikely that you could credibly declare that you could design and construct them in compliance with BS 7671.