Having your connections inside is always going to be better than out if you can. If you're putting a 16mm hole in buy some rigid 16mm pipe and hammer it through the hole. Silicone is not really necessary if your hole is angled so the water can't enter, once connected shove a bit of paper/kitchen...
You don't turn the heating on until you've refilled the system. You'll need to fill the rad with water first, either filling with a jug from the top or using the fill loop on the boiler
Fill loop valve looks partially open, needs to be 90 degrees to the pipe (fully horizontal). There's often one on the other end of the flexi too, make sure that's shut.
I'd suggest one like this that comes with a valve and new back nut/olive. It's unlikely you'll get the old olive to seal on the new fitting.
https://www.screwfix.com/p/essentials-flexible-tap-connector-with-valve-15mm-x-1-2-x-300mm/3558g?ref=SFAppShare
It does mean you'll need to get the old...
Your problem is the depth of the fittings, those elbows are probably about 2 inch deep. You'll be lucky to get that into the cavity never mind clipping it. Solder ring fittings, pipe clips, length of copper pipe and a couple of couplers, will cost about £20 and it'll be rock solid when you come...
Wouldn't worry about it, it has a noggin below and is screwed into the 3" stud. Drill from the 1.5 side though so you're bang in the centre of that. Drill down on the angle so you can bend to your mixer pipework easier. As I said, I'd make up copper L pieces with solder elbows and clip them to...
If you're coming from below come back up the left and just drill through the stud above the lower noggin. Just make sure not to hit it with your hardie screws later.
If you're not worried about supporting the mixer bar then definitely taking the cold onto the right hand cavity is the way to go, then at least you're central to the bath taps and the riser is supported. It doesn't need to be difficult, just make a hole through the vertical stud near the ceiling...
The pipe centres are 6" apart, you don't need to chop any out. You need to get your cold feed on the right hand side of the central stud though. I'd also add noggins (the crossmembers in your picture) on either side of the stud where you want the mixer valve and use your template to mark pipe...
I wouldn't recommend amazon for electrical items, better getting something from a UK supplier. One of the requirements of selv is to isolate the mains earth from the outgoing supply, it would be easy to see a scenario where a cable comes loose and touches the metal casing of that unit. I very...
Yep, youll probably even have space to secure it to the underside of the joist with a clip to keep it tight and out of the way, or all round band if youre putting oval in your chase.
That sounds crap. Honestly watch this video. Fit your isolators to the drops and you can then connect your pushfit pipework further down. You'll need a length of copper pipe and a bender if you don't want to solder.