Think i have found the correct locations.
The picture listed in the haynes workshop manual page 1A.10 calls this the filler but it looks to be the drain plug.
The filler looks to be located higher up at the back of the gear box.
The picture with the drive shaft shows the drain plug 17mm hex in the lower section.
Other picture shows the filler plug just sticking out at the rear of the gear box.
Will give this a go next weekend if the weather stays dry.
Hipcity's post in Transmission drain plug location was marked as the answer
