Jcb 3c mk111 oil leaking from lower chassis

[MrF]

I have a 3c3 with torque converter, but from the discussion around clutch pedal, its not the same one to comment/take pics of what I have.
However, the helpful Mark Rive a way back posted all the part numbers & sizes of the core plugs for the 4/98 (I've had to do a few of them over the years but the place I bought them from last time no longer lists them).
Here's what he posted :-

Cylinder block: 4 x 835/10020 5/8" (15.75mm) 2 x 835/10021 1" (25.4mm) 1 x 835/10022 1.1/2" (38.1mm).
Cylinder head: 3 x 835/10023 1.5/16" (33.33mm) 1 x 835/10021 1" (25.4mm) as above.