Update: TLDR version: I got it running.
I cranked it a few times and it came to life a couple of times but each time spluttered out after a couple of seconds. Checked the decompressor and valve was working. Took the carby off again but this time the O ring for the inlet manifold just broke away so replaced that. I recall previously the carby was reluctant to go back on. While there also replaced the O ring where the inlet manifold joins the engine block. This time the carby went back on smoothly. All back together and after a few cranks it started and kept running. Let it run for a few minutes and didn't stall. So in the end was compression issue. Lets hope it runs next time I crank it up.
A couple of side notes:
1) The decompressor for this victa edger model is different to the decompressor for a mower. The valve is longer so you can't do a swap between the two. Not for this model anyway.
2) The pull cord is located at the front and I had to really yank it and maintain the momentum with the cord fully extended. The pull cord on the mower takes less effort.
