Good day peeps, wet tank syndrome, bloody found it... Any repairs been done before, if I can repair it rather than replace as it all functions really well. Barstool!!
Could try the Plumb centre? Or maybe something like Quicksteel? Given the hassle and the state of it I'd change and maybe keep the internals for spares.
Sorted it. Both the pump and gauge work without issue, the outlet has been wire brushed inspected and a coat of grease. The return has been removed and fitted with fuel tube and o'rings around the outside to seal it. Tested under the bus on the floor. 0 leaks..