Mr Punter

The only concern with FMB would be if they were claiming to be members but were not. You have done decent research. Did you get 3 quotes? If not, make some calls. It is going to cost you a lot of money, so make sure you choose someone who is good and you get along with. You don't need to be mates, but there may be potential differences that will need resolving.

I have used a chop saw. One of the Evolution multi material ones. Goggles are a must.

Have a look at D-Line. They claim to be softer material and may work for you. https://www.screwfix.com/p/d-line-tsb35w-2-2-gang-surface-pattress-box-35mm-2-pack/143cy#product_additional_details_container

OK he did say But I think you are right.

Sounds like your warranty company are being dickheads. Is this Protek?

Yes the sun and wind will dry it and that will prolong the life considerably. The concrete pillars will help a lot too. 20 years is very good.

Decking looks OK when it is first installed but with softwood it does not last long. I doubt the timber screw piles will be very durable.

Have you used washing up liquid? Maybe the air treatment has made it bubble up.

The US and Canada like imperial. Timber frame with studs at 2 ft centres, timber sheet material being 8' x 4'. It can make it easy to set out. I doubt many use imperial weights, other than for people eg 5 foot 8 and 18 stone = fat bastard etc.

+1 Mot, crushed concrete, terram. Dig out the topsoil over footprint +2m and get rid. Make a nice clean road in.

My understanding of the Compriband system is that you have a vapour impermeable membrane - such as adhesive tape /EPDM - stuck between the frame and the structure before the plasterboard, insulation in the gap - like closed cell expanding foam, them Compriband on the outside. This means no internal vapour should get between frame and structure, frame is not a cold bridge, window is sealed from outside weather and any moisture the gets in can escape externally.

You can tell by giving it a prod with your finger. If it is fairly stiff it is compressed. Soft and squishy and they should have used a wider one. Also, make sure it is proper Compriband, not a cheaper lookalike.

I have got stuff from AliExpress and it has been crap. Not working, doesn't connect, chews through batteries. Cheap shit from China.

To do this properly, strip the plasterboard, insulation between the rafters to leave a 50mm gap beneath the felt, 75mm insulation under the rafters, plasterboard. A bit of a pain but it means you maintain good loft ventilation and prevent associated mould / damp risk.

There is a good reason that stair nosings are rounded. Those look lethal.