JohnMo

That sounds a lot, are you sure? But if correct, you will need an additional expansion vessel. Too much expansion room is better than not enough.

Are you having a battery also, if so you need a strategy of what you are doing, as big is better to a point. You maybe better over clocking the inverter with loads of panels, so you have max output for longer periods during a day, and get battery charging as well as max exports. Lots of ways to do this even with a G98 limitation.

We are in a bungalow and have an internal corridor, we have two small roof lights only and it's surprising how much light the bring in. Other ideas, at the leading edge of the roof windows build up a wall and place the roof in windows higher, so they are at window cil level. Get natural protection. Same window just install higher. Question - Realistically will you ever use that space, when and how. For me and our household we never would. I would really look at the reasons for even doing this, not cheap, not easy, maybe never used space.

That's a better use of your money, looks like you have a huge garden, so may make more sense. We had a basement in one of hire properties, a pain in the arse is how describe basements. But depends where the water table is etc. On one occasion the sump pump failed, and it filled with water - fun - not. But be careful with sizing so you don’t overheat the place. Yes to all the above

Maybe not the best statement

To quite frank, if your new build needs more than £7.5k you are being screwed over anyway. So really wouldn't worry or get bogged down with it. Really wouldn't bother with the grant anyway - and didn't. Heat pumps aren't expensive, and you can build a nice simple system not bogged down with MCS bells and whistles.

Why? Required, or choose to?

Whatever, I'll keep doing what I do, as I said never had an issue.

Maybe something like this in reverse. Slope thing slightly to run off to the gravel

Don't do as I do - do as I say, comes to mind. Not much different from a multi millionaire pop star, movie stars, telling everyone to dip their hands in the pockets to give to charity.

There is a roads document that details the slopes required and where the acro drain is located so you don't get slippage on to the road. It basically has to comply with highways regs. Your slope itself is likely to have to SUDs compliant also

We had a full landscaping plan, but at time of sign off most hadn't been done, BC had zero interest, just interested in the actual house build was over plan. Being anal. Your agreed plans for planning and building control, is a legal document. You are not allowed to vary from the agreed plans, so actually installing frosted glass where it hasn't been stipulated is a breach of planning. Prior to doing so, you need permission. So a throw away statement from planning means nothing really.

Really depends how you do it and roof overhangs etc. if required and acro drain will just move the water away out of harms way. Just a matter of planning what you need to do and implementing correctly.

Really wouldn't bother, tech will change by the time you get it working. Or you will change your phone it it won't work.

Only one access point needed. But we have flat access to every door, either on to decking or patio. But whole house is single storey so why not. Nice future proof, you never know what's ahead of you or your family.

Assume NI same as rest of UK and the unvented cylinder would require a G3 certificate to cover the unvented cylinder install. The heat pump install would be asking the commissioning person for a commissioning certificate.

We don't have edge as such. Small step down to gravel

What is an inverted heating system?

Pretty much exact same. Hep2O will also go into Tectite fitting

You also will need to a ramp down to your parking area from that. I just made a very shallow incline direct from parking area to the level threshold in paving slabs. Never found weed suspension membrane to work. The weed are generally blown on the wind and find their way in from above.

Never seen a need to tank a shower room and in my 60 plus years and never seen an issue. Only ever used moisture resistant plasterboard around the shower and normal elsewhere. Tiles direct to the plasterboard. If you foam the plasterboard on or batten and screw it's not going anywhere quickly.

Pretty wide range of pricing there.

Integrated multi outlet or all mounted. Should be easy to do if you plan ahead Cool Energy do fan coils for bathrooms, with towel rail also

Why go mlcp, and not just Hep2O? Hep2O is easy to get, pretty idiot proof (that's why I like it) and no special tools needed. Mixes with copper easily.

Well you have answered your own question, as you have already sorted out your storage of the bits. Why build that big, you must rattle about in there