Well, what a nightmare I have had getting the crank gear off.
Spent a whole day with various pullers and levers, trying to get the gear off but to no avail. I ended up having to fabricate a home-made puller with some threaded M5 bar which screwed into the holes on the face of the crank cog.
Even then it didn't quite go according to plan, and one of the threaded bars snapped, but with a bit of perseverance and some brute force it finally slid off the end of the crank!
Upon inspection, the crank is fine (very lucky!), it was the woodruff key which had got mangled, which is why the crank gear was so difficult to get off.
Here's the pic's:
Thanks to Trailerfitter for suggesting the following video he made: