Mr Punter

Everything about that looks crap. Even the soffits look pissed.

If you cut the timber to the lengths you want, rather than have a few mil difference in opposite sides, you can just screw it together and square it by making the diagonals the same length.

How about white sand and normal cement? I have had to get sand delivered from Cornwall to get the mortar colour looking OK.

Shop around for the warranty.

I suspect you will end up more than £2000/m2 but if the location is decent it will still work out OK. It is hard to pin down costs, but having decent ground conditions and access will be helpful. The work packages may appeal to contractors as there is enough to be bothered but not so much that it will swallow too all their resource. I like the stone wall bisecting the house. I did similar-ish with a brick wall on a bungalow a few years ago but did not go through the roof.

I think it would need 60mins protection, so 2 layers 15mm or 2 layers 12.5mm fireline.

Just bear in mind that if / when they fail and you will may have to do a lot of searching to find something else that will fit.

I have used Estimators Online for guide figures. They are very good value and quick turnaround. It also saves having to measure drawings for quants. I sometimes send their figures to subbies for quotes.

Velfac have a metal outer part which is in front of a timber inner part. The weather seal is between the timber part and the structure.

Yes. It may be easiest to get the original surveyor to do this. You supply plans and spec and pay fees. Are you leaving the brickwork exposed in the extension?

Looks like Velfac / Ideal Combi type windows / doors. Compriband type perimeter seal. Is there any at the top? Slip with a grinder scuffed the brickwork. What did not look right to you?

Some do, most don't, especially those for small resi projects.

I prefer normal render (sand:cement:lime) painted to the through colour or monocouche types. Often it is good to have a coat of bonding material like Rend Aid to get a good key but depends on the brick. If you are doing external wall insulation you would need a different system.

Yes, get an SE to do this, especially as you have a fairly large span and are asking for consideration of more cost effective construction and confirmation of beam spec.

LVT sounds about right. Tiles seem cheap. Make sure they are porcelain.

I think it would be worth getting a demolition firm in to do this. Worth checking them out on the HSE database https://resources.hse.gov.uk/notices/search/standard/default.asp and do make sure they have insurance and RAMS.

I had a similar issue and connected a hose to the pipe inside the boiler and ran it through. Go steady at first, then increase the flow.

Have you priced it in brick or block? I think it would be my preference and no need to worry about distance to boundary from the fire POV.

If it is just for a pair of doors the opening sounds quite wide. You may want to have ones with sidelights. I doubt there will be much difference in price if they are made to measure. Just a matter of shopping around.

Before you clad it, try some brick acid and jetwash. It won't help with plumb but it can help the crappiest of jobs look acceptable. I have seen oil applied to blues as a finish but not sure how long it lasts.

I think it needs ventilation. Your pipe and extractor could be good.

Does internal conditioned air get into the light well?

Yes you may as well for the very low cost. Slab will be moist for a long time.

Yes, split the outer leaves where they hit the glass.