Miek

Polytunnel plastic could work, it's mega strong but it needs to be pulled taught over a wooden frame and held in place with nailed or screwed battens which in itself is a fair bit of work compared to sawing down a sheet of ply or OSB.

I don't suppose you have a pic you could post? I want do bury my vortex pump unit too so keen to others solutions before I freestyle it.

What's the problem with doing as recommended in part H? I would ask building control about deviations from part H. Might be ok as part H isn't actually the regs, just an approved guide. I've just fitted a Vortex STP and when I did the calcs for the drainage field I realised it was going to cost more than the STP. Luckily I can discharge to a nearby water course, though you need approval from the environment agency to do this, or NRW in my case

That pic is a Stihl shredder blade and will cut most things, but I use it on a 45cc motor , I don't think it will be very useful on a cordless tool.

What kind of vegetation are you hoping to cut? Brambles need a curved blade so you can push the tool down on them from above. Straight blades only work in the horizontal but are good for lower vegetation.

Does the slab have to be over the top of the inner course? Can you not continue the lightweight block up to the sole plate to create a thermal break? Maybe use a course of foamglass perinsul below the timber sole plate? These details should be known before you started IMO

Airtight expanding foam might help you. fm330

I had an old 10" radial arm saw, a DeWalt 110 I think it was. Very useful saw, but mine was underpowered with only a 1kw motor, so I'd advise getting a newer one with a bigger motor and going to 12* blades. They seem to sell quite cheaply secondhand, but they are heavy beasts, not portable.

300mm full fill cavity, gets you to passive standards. That is what I'm about to do also.

Exactly how I did it. And use string lines with nails on batter boards.

Try using decent posts? Treated to UC4 standard. Creosote treated posts are the longest lasting I think. Bog standard fence posts are a false economy IMO. Metposts won't last that long, unless you can get hot dip galv ones perhaps?

I don't see why you can't treat it in situ. What fixings? If screws then you could remove it, if ring shanks then definitely leave in place

If you just slab through a trunk (plain sawn) everything except the slab through the centre will curl, not the end of the world but bowed timber is hard to work with and ends up being wasteful. Quarter sawing reduces curling so gives better quality timber. Takes more time to do but worth it IMO.

I've milled a few ash and oak trees with an Alaskan mill. My only advice is QUATER SAW THE TRUNKS this will add more value to the timber than through sawing. A good jointer planer will cost more than 200 quid secondhand

In Wales (not sure if it's all councils ) there is a thing called the One Planet Development which promotes this kind of thing. I know a few folk involved in various projects in West Wales http://www.oneplanetcouncil.org.uk/

The sums for a GSHP might work out if you have a big heating load. Most folk on here discount it and go for ASHP but they tend to be building well insulated houses and the capital cost of a GSHP is too high for the relatively small gain in COP. Also space is a big issue of course. Tapping in to an old well .... If the water in the well is not flowing then once you have pulled the heat out it will take a long time to replenish. I think you need flowing water for decent heat extraction. It might be a huge well though.

The long and short of it is that however you heat it the house is going to use a ton of energy. Most old farmhouses are like colanders in terms of air tightness , and at 300sqm you will need a large heating system. If it's a cold roof then before you insulate the loft spend a lot of effort trying to seal up all the gaps in the upstairs ceiling, there will be hundreds! No point insulating a leaky ceiling IMO. Foam gun & tapes will be best for that.

Might be so, some European pumps use 1" or 3/4” BSP fittings, obviously need to check the fitting accurately.

You can use a regular circulation pump if it's a sealed glycol system , but, it will degrade somewhat. If it's an open system then you can use a bronze body pump. £300 seems stupid high, I'm sure you can get solar circulators way cheaper than that.

Not a lot, however it's slightly more efficient to run a gas boiler central heating circuit at a lower temperature so bigger radiators will allow you to do that . If the return is below 50 degrees (ish) you get the boiler running in condensing mode.

Plastic guttering varies in quality considerably. The very cheap stuff is , well, very cheap, in every way. I'll be using metal, having seen the Linda stuff I like the quality of it.

These guys are very good IMO https://miniexcavatorcentre.com/

Some makes charge extra for seals. I've just bought JDP ones and they come with seals, but to be honest I'm not sure why they have them.

Must be a big'un.

Power float the floor flat so you can roll a jack around easily. I did this and it's great. Very easy to sweep up too.