I had two copies of the rear right leg, so I trimmed the 'plug' very slightly and glued it into the rear left hole with plastic glue. With a small pea sized amount of greenstuff, I filled the remaining hole, and smoothed in slight crenelations with my knife to match the body.
The second picture shows the middle right leg which also needed to be fixed. No trimming was needed on the 2nd leg, just glue and a dab of greenstuff.
This whole thing took about 10 minute so while this isn't a great step-wise tutorial, it should give people the confidence to fix this themselves since it's SUPER easy with no special tools needed.