What should I ask builders when they come round to quote?

[broomers]

DH and I are having our kitchen and diner knocked through and have got our first feed building companies in to quote next week.
We have structural drawings already done.
This is the first project like this that we've done and I usually take the lead on anything DIY related.
Can anyone give me tips as to what to ask builders, so far I have:
Price
Payment schedule
Timeline
Will materials be kept on site (we have a big garage for this)

Any advice welcome!

Will they be installing a portaloo for their staff, or are they expected to have access to your loos?

That's a good one thank you, we do have a downstairs loo that won't be affected by the build but good to think about if there's a load of guys on site and our young children are also having to use it!

Hopefully bump for any more advice!

Ask them for proof of insurance

References
Examples of previous work
Insurance
Health and safety - attitude towards (you do not want the people who try and get away with not using scaffolding!)
Liaison with building control
Who is managing the project, liaising with contractors etc - builder does everything and what does this cost (ours charges 18% but takes care of everything), how many does he directly employ? Any problems getting labour or materials?