Thanks that's very very helpful.I'm pretty sure it has a reducing set therefore you "should" be able to just dismantle the fitting, remove the reducer and reassemble with 22mm copper and a new 22mm olive.
3/4 inch - so a 3/4 olive in a 22 fitting will workIf I recall correctly, Black alkathene was 22mm (a lot of the one’s I’ve been to have been). If this is the case then a 22mm stopcock would suffice.
Yes it does - that's a 22 coupling with the reducing set. The clue is the shape of the nut on top - changed from flat top to shouldered when metric came in - when I started plumbing as it happensThanks Denso, I'm wary of dismantling everything and then finding I can't put it back together again
Here's a closer picture - does this help?
3/4 inch - so a 3/4 olive in a 22 fitting will work