As for NI LR indies, the only one I know is on College Lands Rd near Moy. Can't give you a rec cos I've never used them. But I drive past there a lot and there's always a shedload of RR and Discos outside.
44 quid at Screwfix, I still have the page open.
https://www.screwfix.com/c/electrical-lighting/cable/cat8960001#category=cat8960001&cablelength=10_m&conductorarea=10_mm_
I knew I had a bag of F-plugs somewhere. I went straight to where I thought they were and there they were. This is such an unusual occurrence I thought I'd mention it.