Gone West

There are lots of ideas on https://gabionsupply.com/ Pumice stone, which can be bought in bulk, can be used for a lightweight filler.

There are examples of thin gabion walls on the Fine Mesh Metals site. They are called zenturo panels. https://www.gabionbaskets.co.uk/gabion/gabion-fencing-system

This calculator reckons 12 tonnes, unless I've done something wrong. https://www.primaryaggregates.co.uk/aggregates/aggregates-calculator

That's right. We had an EPC A and when we sold our place we had people bidding against each other for it and we got significantly above the asking price. We were told it was because there weren't PH on the market.

I think it is fairly straightforward, if in doubt, don't do it.

You can have Lindab with a paint finish on top of the galvanising. We had Lindab with western red cedar cladding and fascias with no problems.

The third house I owned was dot and dab and taped and it looked fine.

I had a similar situation and used concrete posts and concrete patterned gravel boards, but it was only 10m long. I have another area about the same length where I am using UBs and oak sleepers.

I have lived in a large number of different houses and I agree that a traditional wet plaster finish feels best. If you can find a good plasterer who can do a good job with a bonding coat and a finishing coat then go for it. Finding a decent old school plasterer who can do it though might be difficult.

For a soakaway, have you come across the idea of crates with 'bio filter media' in them to further reduce the toxicity of the effluent. IIRC it was something that I discussed with my supplier many years ago.

I don't know what the actual requirements are, but when we installed our STP in 2010 we discharged to a Klargester reed bed system. Several years later the supplier said the effluent could be discharged into a soakaway. As the reed bed system was quite high maintenance we installed a soakaway.

I wouldn't use a Biodisc. The local farmer had one and it was always breaking down, and it's a grim task sorting it out. There are plenty of STPs with air pumps, which is what we used. Good luck with the job and I hope it finally gets sorted out for you.

Quite a lot of wood treatments are available in sample or tester pots, so I think your best bet would be to try different types on a small area of a door until you find one which is suitable. Do a search for wood treatment sample pots.

They used the box for sleeping in during the day and they hibernated in it during the winter. We put ours under a large shrub, but if yours like the bamboo area then put it there. Your boxes look much better constructed than mine, so they'll probably be queuing up for a viewing. Put a trail camera there so you can keep an eye on visitors.

We were on a narrow single track lane and I wanted kerbs laid along the length of our site to stop runoff from the road. I didn't ask anyone for permission and just got a company in to do the work. That was in 2015 and they just used a couple of signs.