Mr Punter

Because you have a detached house, the rules now allow you to build a very large single storey extension without planning consent. One benefit of building single storey is that it won't cast such a big shadow over the garden. Would it work out to have a very large family room at the back and perhaps repurpose one or two ground floor rooms as additional (en-suite?) bedroom(s)?

The work needs to be done neatly and carefully or it will look crappy. Obviously it won't match the neighbours. By the time you have arranged safe access (scaffold) are you sure it is worth it?

Not sure how the prices will work out but you normally have aggregate either delivered in tonne bags via hiab or tipped - 10 or 20 tonne. I have only used a grab lorry to take away unwanted spoil. The crushed concrete is fine for a subbase but the crushed limestone type 1 MOT binds together much better and could almost be a finished surface after it has been rolled. For price, ring round a few places.

I don't think you will get a meaningful amount of insulation in there. How wide is the cavity, and is it clear from obstructions?

Sparky fitted an 80A fused switch in the kiosk with meter tails. He will run SWA sub main underground from the fused switch to the consumer unit location in the property and connect up when we want it to be permanent.

Where we are they (UKPN) like a GRP kiosk. I got one of these https://www.ebay.co.uk/itm/192594789689 and have a CU in there for temporary site supply and it will be made into permanent later.

Be warned that bamboo can be very invasive. As others have said, you may be better screening the areas locally rather than attempting a high barrier at the boundary. A well planned layout with a pergola and some focal points and trees, shrubs and paths will be lots better. It can take a while to establish though. I did this one about 25 years ago and there is a very large building all the way along the left hand side.

With soleplates, steel column bases etc it is normal to get them in place then level them to the correct height with packers and then fill the voids between packers with structural grout or dry pack. I would have thought the same could have been done for the doors.

The planting on the bank looks good. Are you paving in front?

You would need to ask them. 50mm insulation won't quite do it for existing but it will still make a fair difference.

If there is no insulation in the roof you may want thicker insulation boards but this can impact on the eaves and abutments.

I have smooth Ipe hardwood decking on Iroko hardwood joists. No slipping at all. I doubt they will rot any time soon.

All you need now is some cement!

Slates are sitting nice and flat. What type are they?

Looks absolutely bonkers and destined to disappointment.

I understand it needs to be toughened and laminated as there is no independent handrail. I think the minimum thickness is 13.5mm but check with the supplier. When they do a system they normally have all the calcs to back it up.

The regs say positive pressure of at least 38mm water gauge for at least 3 minutes. For below ground pipework it is 100mm.

No they sometimes do it, sometimes not. Certainly been around for the last 25 years.

Is it obvious, or have they already sussed it? If not obvious, some blue loo cleaner could help disguise. I am quite surprised that wire wool would case much damage. I also doubt that on the basis she got a full scholarship she is anything other than very clever.

The concrete angle ridge tile with dry ridge fixing system works fine.

It will be so rare that you need any heating in bedrooms if they are upstairs. The heat from our towel rads more than heats the upper floors and our place is fairly standard insulation and airtightness. The cooling could be useful on the odd days when it is really hot and it means you don't need to have the external blinds down all the time and be in the dark on a nice sunny day.

This sounds like it is outside building regs so maybe don't bother. Unless you are in a really exposed location the roof will help hold it together. Use restraint straps on the rafters.

How were the drains?

Are you buying or selling?

Nice job! You could dye the wheels piss yellow to match the feature grout.