Ok guys, thanks for all your replies.
Well I have had an electrician friend take a look and he reckons a full rewire is needed (though of course he'd say that). We talked about the design, and where I wanted everything and he's going to send me a quote.
Now on our first meeting I told the electrician that I would lay as much cable and do as much chasing as possible, and that I only wanted him to do the minimum that he legally has to. On his second visit he was talking about how he and his colleague would lay cable here, chase cable there. So I was like "Woah there, I told you I would lay cable, do chasing etc". He told me he should do it because he can get the materials cheaper, or I might make a mistake etc. I told him to give me one price for him doing the lot, and another price for me doing all the donkey work. He seemed reluctant to give me this second price TBH (I bet he doesn't).
Now maybe I'm being cynical, but I suspect he just wants to earn more money from the job, hence disuading me from doing the chasing and routing myself?
He has a point that a mistake may be made somewhere, but I plan on hiding the cable behind 2 inch deep skirting all round the perimeter of the flat, and just chasing up a few inches to the outlets. I would leave all this exposed (i.e. no skirting, or plaster on) for when he comes and does his bits, so any problems can immediately be identified as all wiring will be exposed and not hidden. I am a mechanical (defence) engineer by trade, and this would be far from beyond me.
My question is, on a rewire, what exactly is the minimum the electrican can do and still be able to certify a rewire? As this is what I want.
And secondly, what suppliers would you recommend for materials?
Thanks.