Ok I managed to get it working…
turns out it was just me not paying attention and being stupid (like usual ). On closer inspection the inbound requests that I was getting were all unsubscribe requests.
This was because me thinking the reason I did not get new requests after a bit was due to accidentally subscribing to the same topic too many times and there for sending unsubscribe requests via postman.
Turns out my subscribe create request was correct but the code around it to read the file I stored the token in was not, which made it not run. After fixing that code and running it again I now received a subscribe inbound request, and the webhooks/subscriptions endpoint shows a subscription.
Thanks for the replies and for your time, and sorry for wasting it a bit…