Grammeretto Go for it. You can rent a small flat for a year and if you are just the client with a professional project manager and competent professional builder, if they say a year, then a year it is likely to be.
I can actually remember a Grand Designs where a lady like you
built her retirement house in her back garden. As far as I can remember ontime and on budget. GD tends to like the big design with unqualified builders and a ludicrous budget because it makes good television, but in this case I suspect age and sex were the points that caught the production teams minds.
If I sound very gung ho, it is because, at rising 82 DH and I are down sizing - to another old Listed building - which will be the biggest project we have yet undertaken. It will all be done by professionals. DH is not fit enough to do it himself, but we face rewiring, replumbing, possible changes to the central heating, new staircase, new kitchen and a repositioned front door. And the only way we can insulate the roof is by taking it off and putting it back on again. I am really looking forward to it!