The CAA are indeed the best people to ask. They are the ones who will give you authorisation to transmit on the appropriate frequency and appropriate power with an appropriate ident.
Without the above, you can't turn it on.
If this NDB is in it's original site then things should be fairly simple. If you have moved the beacon then the CAA will have to ensure that the DOC is appropriate.
As for the actual comissioning process once you have CAA approval to switch it on, there are no flight test requirements for NDBs in the UK. Only VOR/DME/ILS aids are flight checked.
The future for approaches is that every approach including private ones will be published and if it isn't published then no one can fly it and that includes holding procedures. Except VFR flying of course!!.
Regards,
DFC