what to look for in a loft quote/company

[alltheworld]

I have had quotes back from four companies and they are all very similar in price.
What should I look for when considering the quotes, or what further questions should I ask?
Things I have thought of so far
Look at what is included
Think about if I want a company that employs the workers as opposed to contracting out.
Look at timescales
The payment schedule
Anything else?

[0hCrepe]

References for other jobs they've done.

[alltheworld]

Thank you!