ahhh ... so there's another bit of plastic which fits to the hose (currently still on the radiator hose in the car) then the two bits clip together and retain with a clip ... right?

That makes more sense. Won't have a chance to look until next weekend now but will be happy to get it sorted.

Cheers

Ok found the time to do the job, easy with your excellent instructions, thank you. That Y piece had been 'siliconed' to the block presumably to try and stop the leak. Cleaned it all up and refitted the replacement. It still leaks!!!

However, I have now got a video of it. It was a pretty 'loose' fit in to that new piece and I just knew it was never going to hold. I assume (maybe wrongly but judging from other forum posts) that the problem is that over time that other bit of plastic (inside the rubber hose) has distorted so I need one of them. Here's the vid ... what do you think?