Tom.
Since you are in England, 'Astec Models' is probably a good place to start. They have many couplers for motor/shaft connection. For both flex shafts & solid shafts & in many varying sizes.
All you need to know is the motor shaft size & the propshaft size. There will be a coupler to fit.
Wooden dowel would more than likely snap within a few seconds & is not recommended.
Here's the couplers.
[link]https://astecmodels.co.uk/catalog/index.php?cPath=1_43&osCsid=b262caf5ac80633865c874 99af8d3b52[/link]

And here's three pages of drive shafts.
[link]https://astecmodels.co.uk/catalog/index.php?cPath=1_90&osCsid=b262caf5ac80633865c874 99af8d3b52[/link]

Something there should suit your needs

Paul.