Did you try revoking Strava access in your fitbit settings and then connecting the correct Strava account?

Yes but it didn’t work, it only wants to connect to the newly created Strava account that I can’t access to delete 

Then it seems your browser has saved somehow information about the wrong Strava account. I would suggest using a private browser window or another web browser for reconnecting Strava so you are not automatically linked to the wrong Strava account. I would also suggest checking which login method you use for your correct Strava account (like email/password or some of the other login services like Google) so you can apply exactly the same method when connecting Strava again.

Thankyou so much for your suggestions, I disconnected everything and restarted it again, using a different browser and it’s worked. Been out for a short walk and it’s logged it on the correct account- I appreciate your help x