Hi
We don't so stand alone loft conversion so we can offer some advice without it being a marketing pitch.
Be very wary of contracting one of the loft conversion/kitchen extension/etc farms.
The problem with that 'farm' approach is that you have no contract with the named company only with the subcontractor who carries out the works for you. The farm takes their % leaving not a great margin for the poor old subcontractor.
That sort of approach might have worked when materials where cheap and good eastern European guys were cheap and plentiful but both of those parameters have now changed: with materials cost inflation through the roof and labour costs having risen steeply over the last 18 months.
Honestly you are better of finding a small outfit and make sure you get some good recent references and can see the work. Ideally you want the owner to be hands on at the site. Construction is hard to scale and hard to manage IRL and there is a certain force of personality required to get stuff done.
- Get the design work done in collaboration with the contractor
- Use a proper scope - define things like the exact model of Velux and slates, felt, timber grades, who will make the stairs and what of. Don't go overboard but a sensible excel with description, #part number, value is all you really need
- Use a proper contract
- Define payment stages with payments on defined phases complete
- Make sure that everyone have proper insurances for the type of work - Lofts are working at height so many standard policies don't cover this.
Good luck
Oh, and if you/they run out of anything onsite you can always go to
www.trade-angel.com
and they will get it round to you in 90 mins and it is cheaper than Toolstation or Screwfix.