I did this about a month ago, a straight off the shelf part but would you believe they didn't give me a full invoice, just a cash receipt?!
I believe they are M14s or the imperial equivalent....
I took a selection of the hose/tube joints down to Hydralink (local, so not much use to you) - they are a hydraulic line/fluid connector workshop which service water blasters and construction plant (diggers/excavators).