Hi I have two Punto Sporting 1.2 16v cars with the same issue. One engine is out and gearbox off. Core plug leaking. Other is leaking water from where gearbox joins engine so almost certainly the same problem.

Where can I get these plugs? What is precise size/spec?

Many thanks
Sam.

pretty sure its this one you need

https://www.eurocarcare.net/various-engine-fittings/ecc55182787-core-plug.html

but do measure it before you order