HappySam

How about this? Fibreglass repair tape; https://www.toolstation.com/fiberfix-repair-wrap/p38594 Use it to create a base for a layer of filler. I did similar on the splitter on my Elise.

Pressing the button to the right of the scroll wheel will bring up the list of displays. Use wheel to scroll through and press to select. Can't remember the name of the one that includes the digital speedo but its there.

No idea if they're any good but there's a few options on Aliexpress https://www.aliexpress.com/wholesale?catId=0&initiative_id=AS_20211011084934&SearchText=dash+cam+skoda+octavia+3

Can't see the point of spending £50 on a plastic cover. I'd buy £10 of vinyl wrap from eBay and stick is on. No one is going to know the difference and it'll be easier to remove come sale time too.

Looking at pictures online, B appears smaller

Agreed. It's not the discs. Nigh on impossible to warp discs. Have you replaced the pads each time? Are they OEM? This would seem the most likely cause.

Correct. 5E0075101 fitted my FL vRS perfectly. 5E0075111 at the other end

I fitted front and rear oem ones to my car shortly after I bought it. They clip and screw into existing mounting points. It took about 20 minutes without removing the wheels (a very stubby screwdriver helped though). You'll need to figure out how to fit universal ones yourself. They're likely to be less secure and unlikely to follow the contours of the car. OEM definitely worth the extra.

Remove the little securing bolt and spin the disc on the hub. Simples

The MOT manual only imposes specific constraints using the front indicator as a side repeater. There is nothing specific about the visibility of a separate side repeater.

I've had the same problem. Generally only when it's been raining for a while and is really wet out. As you say switching it off and on generally clears it (turning CC on while the engine is off helps). There's a few threads on here about it so quite a common issue. Some resolutions include changing the stalk but this seems like moisture in a sensor/connector to me. I'm going to reseat the wheel sensor connectors when I take the wheels off to paint the rusty disc hubs. Whether the dealer can fix it or not depends, like so much these days, on there being a fault code present.

Genuine roof racks go for peanuts on eBay. I paid £30 for a pair when I got my Octavia. They're bars in the video so assuming that's what you mean there's a pair on eBay for £9.80 with 21 hours to go and no bids (+£8.50 postage).

I have a BlueSkySea B1W hardwired in my Octavia. Absolutely no problem with DAB. I used a Nextbase hardwire kit (carried over from my old car) as I found cheap ones caused issues and simply failed to work when it was really cold out.

I've just replaced all the interior bulbs on my new to me Octavia. I bought the 5 LED version of these for the interior. They're bright enough and dim OK. I got some 9 LED ones for the boot but they're too dim so I took a punt on these for a tenner instead. Again, they arrived pretty quickly (I only buy from sellers with decent feedback shipping from the UK). They're plenty bright enough for the boot and even better value now they're £8.