Wheres the water coming from ?

Good so far, but this wouldn't have drained the hot water storage cylinder. The hot outlet & open vent are from the top, so the cylinder is still full of water, despite draining the hot water pipes. To drain it, you'd have to stick a hose in the top and siphon the contents out a window, or use a low-level drain c*ck if there is one.

This water shouldn't be able to get into the heating, so the likely cause is that the coil is leaking. Drain the cylinder to confirm this; the water should stop. If so, new cylinder time.

Probably a lucky discovery, it would rot your radiators very quickly.

PS And you DID switch off/isolate the immersion heater, didn't you?

which bit of "Drained the hot water cylinder and heating system " did you miss? (the new cylinder is in place (empty) awaiting final connection)

Wasn't wired up, and thats where the leak from the old cylinder was causing all this work :-(( (well near it, actually the copper cylinder had sprung a leak)

Just to clear this up, drained from stock c*ck at lowest radiator in Kitchen (boiler and cylinder on 1st floor, water tanks in loft) New cylinder appears to have water in heating coil not the hot water area of the cylinder. its in the heating system side of the pipework, not the hot water side. thanks

What did you do with the upstairs radiators when you drained the primary system? They probably remained full unless you opened the vent screws. But, unless both valves were turned off firmly on each rad, some of the water can later slowly gurgle out.

That was my original though - possibly due to a TRV opening as it got cooler.

Vass had previously written:

Doesn't the water coming through your kitchen ceiling suggest to you that some part(s) of your previous statement may be incorrect?

Keep at it, Sherlock.

Ah ok yes I missed that bit, did'nt open any radiators so this is the probable cause will empty everything and check again Thanks

Whenever I work on my system, I turn all the upstairs radiators firmly off - both ends** - to keep them full, and it's surprising how little water comes out of the pipes.

Don't forget to mention to the missus that she mustn't turn them on!

The immersion heater failed, so he replaced the immersion heater.

In removing the immersion heater he wrecked the cylinder, so he replaced the cylinder.

In replacing the cylinder, he flooded the kitchen.

I'd recommend calling a plumber.

Surely if he carries on as he was going he should now replace the kitchen?

I await further requests for assistance with great interest.

Is there a DIY equivalent of "There was an old woman who swallowed a fly . . ."?

Far better is the Flanders and Swann musical version "The gasman cometh". ;-)

That's very funny - but it's not quite right! That's a circular sort of thing (like "there's a hole in my bucket") - whereas what is needed is something which escalates at an exponential rate - maybe starting with changing a light-bulb and ending with a heap of rubble where the house had used to be!

The gasman will often achieve that.