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.
I've just retired as a plumber/heating engineer but I remember that one of my first self employed jobs after leaving college was replacing the siphon and fill valve on a close coupled toilet. It seemed that everything that could go wrong, did go wrong. Don't remember how long it took but it...
Looks like a redundant fitting which could be removed. I would also get the bodged up sink waste replaced as this is also likely to be a leak source. Fitting a good quality sink waste/trap correctly is not difficult but I've always been amazed at how many are done badly even by professionals...
They will need trimming back a bit further or maybe the pipes will push back before tightening. Anyway, it looks like the job is unfinished. Not unusual to leave the pipes a bit long until final fix.