Is a lot simpler than changing the pipes. Take the radiator off and you should be able to take out the black rubber block inside the radiator on the left hand side. Re insert it into right hand side job done. There all
Removable usually. You can always ring the manufacture and find out. Will...
One way to check if expansion vessel is faulty Is to take of the plastic cap and push finger on valve, if water comes out then the rubber diaphragm has gone inside expansion vessel. If it’s a pain to change expansion vessel inside boiler then you may want to think about fitting a new expansion...
The cold water should be gravity fed as well but a balancing valve would work. Also does the hot water come through if the cold water is isolated to the shower pump?
Attach flexible hose with a 1/2” male iron to 15mm Compression to this elbow tap connector, attached in link.
https://www.screwfix.com/p/angled-service-valve-15mm-x-/66255
You have come off the top of the flange to the pump it should be the other way round. Out the top of the flange should be your vent and the horizontal outlet of flange should go to pump.
I use poly pipe silicone grease that’s in a little tub, I also use the spray which I use for speedfit fittings but it’s not as good as proper grease. Hunter do a grease which is slightly more runny. All in all it depends what your using the grease for? If your using it for drainage fittings and...