Found a solution, a bit of a kludge, but it works thanks to another Tom in this post.
My marketbindings.sh:
#!/bin/bash
# Australian BOM Binding
curl -X POST -H "Content-Type: text/plain" --data "id=market:binding-4491519" http://192.168.10.100:8080/rest/extensions/market:binding-4491519/install
The startup rule (relevant bits anyway):
rule "Startup Rules"
when
System started
then
Thread::sleep(30000)
executeCommandLine("/etc/openhab2/services/marketbindings.sh")
end
Hope this helps others and thanks to you Tom and the other Tom for the idea.