Where in the Borders are you, I have these two Wipac, 6 inches diameter, glass front, plastic back with wires and mounting bolts. Make me an offer, I am in Coldingham.
Its hit or miss with Britpart. they are not a manufacturer but a firm that buy cheap and sell cheap but some of their stuff is original equipment, just depends on what they can put their hands on. Or so I am led to believe.
Oil is in the centre of your axle which is obviously hollow. The oil should only get as far as the inner part of the outer end of the drive shaft and is stopped by gaskets and a rubber washer. If any have deteriorated then oil will leak past and into the cover for the swivel ball as shown in...