Hello John,

The best way to approach that is to have an idea of your budget. If the works are now largely already done and it's just the above things you have mentioned windows and doors. Then consider what materials you want.. What windows.. Wood, Crittall ?and then get at least three window manufacturers to estimate and cost. With doors... You could get reclaimed rather than new...

If you want a kitchen you can find someone who designs and suggests procurement wise... Also consider pre-made shells with different doors. You could have reclaimed cupboard fronts on a manufactured casing.. Or hire a chippy to make the fronts with carved handles rather than knobs and metal ... There are lots of ways to shave and save! : ))

Hello John, sorry, your questions are a bit vague.Where in the country are you based? London and the south will be more expensive than further north. If it's mainly internal fit out + new windows and doors [and roof windows] allow about £1650 + VAT / square metre of gross internal floor area. This is based on one builder completing the whole project for you for one lump sum and also based on mid range quality of build and finish. Obviously, if you are after high quality bespoke then it will be a lot more.If you are sourcing materials and organising trades yourself this will reduce costs but add to your time required and hassle factor.

Assuming you are after mid range stuff then Howdens kitchens are ok as are some of the internet bathroom suppliers.

Having looked at your plans briefly would the new drain run from the ground floor wc be more straight forward if went out to the right and down the parking driveway to the manhole? I assume the existing factory floor is concrete and therefore you will have to break out the concrete for the new drains?

Hope this helps.