Appointing a builder - practicalities? Please help if you have experience.

[DillyDot]

I'm about to appoint a builder for major (structural) work on my house.

I have a quote that I am happy with with a reputable and long established company - but what next? What do I need to ask them or do before I sign on the line and we start work?
I'm thinking:
Insurance (theirs and ours)?
Mortgage company?
It doesn't require planning permission but building control will presumably want to know (or will they deal with that?).
Payment plans - what's reasonable?
Anything else?

Please help! I've never done anything like this before.

I think that's a good list. More detailed than mine.

Time scale of the project?

Never assume. I once had a builder adding a whole floor to my house. Quite a detail costing, we talked about timescales and payment schedules etc. And I remember talking with him quite a bit about the stairs, as in the end it had to cut across the window.
What happened: I didn't specify quality of things; the switches and sockets were the cheapest. And amazingly, the staircase was an extra! Added significantly to the budget but I had 'assumed' it was part of the rest of the build.
And be there daily- if you are not there to answer questions they will just guess. That's why I ended up with sockets in a closet- I had marked them on the floor plan meaning they should be in the hall, but the builder thought it was the other side- in the closet! Like, why?
Material costs are rising and rising so have something in the contract about that, like a cap or something.
Builds always run over - try and put a penalty clause in.
Make sure building regs are informed - you may have to pay the fee direct. They are essential.

Thanks - these are helpful. Perhaps I'm more organised than I thought?