Ok a few qu's - how old is the house? And wat are the walls made from?
If it's roughly Victorian it will very likely have lath and plaster throughout. This can be a complete crumbling nightmare when you have to put in sockets.
Our experience was that we hired a young, enthusiastic guy who mainlined caffeine energy drinks, was bright, chirpy and helpful BUT he was a scatterbrain and he had very little experience in an older house. Well, one as crumbly as ours anyway.
I didn't want to hire him because he seemed to young to handle it, and I didn't think he would have enough experience, but the family decision prevailed.
To cut a long story short, I had to reset every single socket and lightswitch (there were about 25) by removing them from the gaping holes he'd bunged them in (sometimes in plastic wing boxes...which came out of the wall when you removed a plug), battening behind the wall, plastering all around and making good.
It was DREADFUL.
Also we had the choice of taking up our laminate floor, which we had partly bought the house because of, or channelling in multiple places up the walls. Having seen one of his channels, which involved trying to grind into rock hard crumbly brick, and the plastic sleeve barely being concealable under plaster - which I had to do myself, too - I opted to take up the floors.
He still left multiple things unfinished and used a 15yo apprentice who got EVERYTHING wrong - so for months we were calling him and saying 'The junction box up here isn't even screwed together' or 'where is the equipotential bonding?' (there was none)
Upshot of my advice is get someone OLD. Someone careful, thorough, tidy, with vast experience of old houses and how to manage the walls - not someone who wants to dart around making random holes and saying 'yay, put some downlighters in here, bring it up to date!' and then finding that they can't for various reasons.
Experience is your watchword.
(ours was about 3 and a half thou I think, for a house about half the size of yours)