Thank you all for your comments, very helpful and informative. The pipes are 22mm dia and these are press fit indeed, similar to the ones in the link to Screwfix. No, I haven’t paid him in full yet. The scope is for a complete replacement of central heating, cold hot water and boiler – a significant expense for me. The house is 60 years old and I would like the new system to last another 60 years. Both the plumber and the system came highly recommended unfortunately it’s a bit disappointing so far. I already had a few leaks amongst the other issues.
Insulation, that’s another topic. I ended up doing it myself despite having it in the quote. It was a bit too patchy to my liking. It wasn’t worth arguing so I’m just installing it myself, the grey polyethylene pipe insulation plus silver tape (those three bits are there to save me hassle squeezing them later as the tubes are quite tight). I just like to leave the tubes exposed for a few days to check for any sign of leaks – like I said I already had a few in the past.
Indeed, this only required little extra time to make it properly. I still have access to it so I’m hopeful to have it rectified, just not sure by whom yet - any recommendations for a good plumber with the required tool in Glasgow area?