So the part is this:

https://www.darwendiesels.com/commo...rcedes.html?search_query=mercedes&results=144

All I did was remove the washer off that connector as they don't sell the washer separately and also removed the rubber o-ring off the same piece as they don't sell that separate either. The connector cost £5.70.

It's very easy taking the connector off as it just pulls out.

Also a link for the quick release connector:

https://www.darwendiesels.com/searc...=position&orderway=desc&search_query=mercedes

they advised that the part had to be ordered in normally takes a few working days and it's roughly £15