Sorry I took ages to reply.
We planned/managed it all ourself breaking it into tiny steps. Then doing a lot of it ourself.
The main thing we did ourself which I wouldn't recommend is ordering and fitting the steels. We completely underestimated how many people it would take to lift them into place. And then also knocking down the wall to join the old and new, which in hindsight was a purely stupid thing to do ourselves.
If I was to do it again, I'd get a builder in to get it up to the point where the carpenter comes in to do the roof. So foundations, walls, steels, and knock through. Then I'd get a carpenter straight in to do a temporary stud wall on the knock-through.
Then from there I'd do it bit by bit using different trades in roughly this order; carpenter (for roof), roofer, window fitter, electrician, plumber, plasterer, carpenter (for internal fit), tiler, etc.
If you do it that way you need a really thorough set of structural drawings, and to prepared for stress, a lot of researching, decision making, and being let down. You'll also need someone that's home a lot to give keys to different trades, brief them in, and be around for quotes.