Thanks for all the info everyone.
I thought it would be overly sided towards getting a pro in but looks like there is room to do stuff within reason.
Ideally yes we would have someone come in and do it all and that is the plan.
Is it fair to say, main circuit stuff should be done by professionals, while something like adding a few lights, changing fixtures over to LED should be fine as long as we know what we are doing?
Personally, I have been working with wiring homes, adding circuits to CUs and replacing them, putting power into workshops at bottom of garden since I was 13. Probably not legal looking at the documents some have listed...
Again thanks for the info. Much help.