Try Tap Magician. Looks like the cartridges you need are £10 each.
https://www.tapmagician.co.uk/NSManufacturersShoppingSelect.aspx?ENCB4AF132333&CDA&TT41
Is this the one you were trying to remove in your earlier post?
It doesn't seem to be visible when the tap is assembled so you may get away without having it at all. If you want to have a go at removing it, try wrapping a few turns of insulating tape round it and then hold with a pair of pump...
Looks like the longer one has been wound out too far and now won't go back as the hex shaped internals have rotated slightly. That's why it will only do one turn before it jams. You should be able to pop the circlip off the other end and tap out the internals. Clean it up, apply silicon grease...
Looks like the hose adapter is broken. Should be this one.
https://www.bathroomspareparts.co.uk/aqualisa-aquastream-thermo-power-shower-2003-current-white-hose-adaptor-kit-241310-9186-p.asp
A nice cheap repair if you can get hold of one. Showerdoc.com shows the part as discontinued and only...
As HB says, it may just need nipping up but water would pool at this point if the valve was leaking from the gland (spindle).
Remove the plastic cap to verify its not leaking from there.
I've known people who love their warm air systems but most find them difficult to live with.
A separate qualification is needed to work on warm air appliances. As these systems are getting older and more scarce, most gas engineers don't bother to get the additional qualification. This means...
Try nipping them up with a pair of grips. Hand tight is probably ok on the low pressure inlets but not enough on the high pressure outlet side
Maybe a silly question but did you put the rubber sealing washers in?
Site rules don't allow gas related advice on the open forum. Safe to say though that your boiler is seriously unwell.
Depending on its age, there may be warranty on some parts so get Worcester out to look at it. They would probably want to see a full service record though. Working inside the...
The fill valve is height adjustable. Here are the manufacturers instructions.
https://www.free-instruction-manuals.com/pdf/pa_3320487.pdf
Can be a bit fiddly removing and refitting the clip. Best to turn off the water before starting.