Thanks guys, I had a carpenter in today to measure up for a custom door and he offered to make a tool to cut a replica (£200), but thats not really cost effective for the 3m I need.
I have some rough old stuff with 120 years of paint on I will clean up/strisp instead and reuse.
To be fair , 3 router cutters will do it . Normally I pay approx £70 for a set of spindle tooling to be made . Which is cheap .
But with a bit of head scratching this could be done easily by hand for 3 metres