The issue is not one of DIYing or not.Clearly the first reply was helpful but those since including your own has really added no value. Simply saying 'ask an electrician' doesn't appear to be in the vein of the spirit of the forum and the nature of DIY.
It is that you are using an electrician.
And that electrician will be required to sign this:
I being the person responsible for the Design, Construction, Inspection & Testing 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, Construction, Inspection & Testing, 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 to declare to your local Building Control people that he did it all and that it all complied with the Building Regulations.
If nothing else it would be rude of you to get other people to make design suggestions and decisions which you then present to him as a fait accompli.
Worst case is that (for whatever reason) you do something he isn't happy with and you have to rip it out. If he won't sign the certificates you'll be up S.C. with no paddle.