I would suggest you need the patio cleaning attachment as well - circular thing with rotating jets. It makes a better job of it.
Then spray with Patio Magic or similar which keeps the mould in control for months.
Use a louver door for the cupboard door - i seem to remenber you can get various standard sizes, then make the frame to suit.
Change to a smart meter - they will check it out when they come to fix the new meter!
Search for "SWAN NECK PAN CONNECTOR" - It may even be too close ! But watch out for flushing problems. I think the Swan neck is designed to go downwards where an the old soil pipe was in the floor so better check if it will work horizontaly.
Well after my other post I decided to make my own radiator "knob". This is the MK1 , I may improve the shape later. This works better than the original, more leverage.
It may be caked with mud or even plaster or cement. This happens when workmen wash out their plaster bucket down the drain ! Try some more poking around.
Go gas ! I understand heating oil has gone up in price far higher than gas over the years, oil fired boilers are probably far more expensive than gas boilers.
You'll save space where the tank is and probably where the boiler is.
Here are pics of the valve and knob. The union to the radiator is bigger than normal and the pipe is 22mm or the old imperial equivalent. It is gravity fed off the HW primary so we need to turn it offin the summer.
On some flue outlets you can direct the flue Left,Right, Up, Down or Straight.. You take the end piece off and twist and put it back on to redirect the flue. This may help if you point the flue away fromthe trouble area.
Reduce the HW on time to a minimum to reduce the effect. I had to put TRVs in all the upstair radiators. Just happens in some systems, a convection current finds its way round.
My bathroom rail/radiator has a larger valve with a 7mm square shank. The plastic knob disintegrated years ago - anybody come accross a valve knob with a 7mm square drive ?
Surely, what you have is a power shower already ? It has a small pump in it and I think it mixes H & C then a single pump pumps the water.
The alternate is one where you have a twin impellar pump sited remotely which pumps H & C separately and then a mixer valve in the shower area.
This looks like threaded iron pipe screwed into the female ends of the stop cock - very tricky. You can just replace the inards if you can find an exact match - you may have trouble undoing the old one. Best if you can find a similar stop cock and dismantle it, then you'll know how it fits etc...