Onoff

Seemingly the stuff above is polythene inslated cable with a pvc sheath to BS1557. So 3-cores, red, white & blue, no earth, Imperial 3/0.29 I think, 3 tinned strands per core equates to about 2.98mm2. It's like new.

Get digging!

I think that traditional, bitumen based, string reinforced roofing felt under tiles, has a lifespan of approx 30 years?I can't imagine in 2006 they used that though? (I know mine done in 1987 is becoming very brittle). Maybe the company doing the loft extension is dubious of the original work. At least if they renew the lot and it leaks then there's only one company to blame!

Screed?

Damn right, much easier to do the former in metal! ?

What's the benefit of piles over a slab with a ring beam?

Not at all. I just dug a 13m trench with one, 600mm deep. No wider than 6". I started off with a pronged digging tool then gave up and switch to the mattock. A revelation. I had to go through conifer roots and clay. Sharp mattock blade will go straight through the roots if you hit 'em right.

Great tool for roots: https://www.toolstation.com/roughneck-mattock-with-fibreglass-handle/p20759?

Search instead in YouTube for Miss Makita. (Miss DeWalt is a munter btw).

Me being a mere youngster ? I'm hoping @ProDave recognises this, red, white & blue, flat cable no cpc: Post Brexit I think we should go back to these colours...

Well... I've come back with two sheds...I think. One is called a "Windsor". Never assembled even. Plus...an old tin bath, various gothic esque pots, benches etc. Sadly I had to leave this: Seriously how 'effin cool is that? Wonder what voltage it put out? Looks like you could put a belt on the PTO maybe?

18 or 40V?

How about stacking a couple of pallets of lightweight concrete blocks in a ramp shape then covering in concrete to form the slope? As @nod said, cover the top of the blocks in a sheet of DPM. You could break it off later and sell / reuse the blocks. As for handrail...3x3 timber posts banged in the ground?

Are all your connections tight? Particularly the neutrals both at the source (where it's fed from), in the cu and at any junctions along the way. You haven't had any digging done that may have caught the supply cable or if overhead the same, or any serious chaffing?

A member here has a super insulated house with 300mm of polystyrene under his heated concrete floor slab (100mm thick from memory). He's calculated he still loses 8% down through the floor. (Don't get me wrong, any insulation is better than nothing).

Tell me! Just whacked the bathroom basin mixer on hot and timed it. 1m to warm, 1m15s to hot ?

It's a Rapier...

What size bolts? What you're talking about is a bit different to how @Trw144 has done it! If going into blockwork I'd be looking at resin anchors.

Here you go, the thread with pics of your stairs:

Same RCD here? https://www.tlc-direct.co.uk/Products/HGCD240U.html

Noted some half finished wiring today in one of the sheds. Twin & earth all red and black. 3 core and earth, red white & blue, stranded cores.

Never a truer word said in jest! Ended up helping out at the neighbour's. Imagine a time capsule of a couple of people in their late 90s. Opening WW2 trunks that came back from India and being told "Watch out for guns!" (Didn't find any ?). I came back with this cute little battery lantern to restore. No glass but I'll figure something out! ...& a shed! Seriously, there's a couple of brand new, unassembled timber sheds sitting in, well bigger sheds!

A bit off thread... Only 2 days later than planned but I finished my Makita battery to Champion circular saw! (Finished the second set of parts to convert the BiL's one too). The saws were bought with two Nicad batteries and charger, in their own case, years ago, at 75% off marked price for £25 when a Focus/Do It All was closing. Never seen much use didn't have much grunt and the batteries died quickly. Not sure how well it will work or even last. (My previous attempt at converting the Rolson 18V grinder to work with 18V batteries looked like it was a winner until the tool burnt out). A quick video at this link: https://flic.kr/p/2kDdSQh I do note the saws no load speed is only around 2500rpm compared to say a modern Makita that runs at twice that. If cheap enough I guess I could try a gruntier motor from Banggood, AliExpress etc. I'll have a go on some sheet material later.

Certainly not from over use!

Lad I know walked in on his MiL holding a broom. "What's up Maureen, can't get it started?" They didn't get on...