Cheers. The local euro car parts only had the 125ml in so poured one of those in and took it for a drive and dropped into the local main dealer to see if they could give me some tips on how to avoid paying for a couple of sensors each year. No sur[rise they had none saying the ad blue system is relatively new so will have teething issues. I then I would call it not fit for purpose as a usable vehicle. He became very disinterested after that and only offered to take my pants down for another 178 quid diagnostic.
I just hope the additive works.