@rakesh-mukundan Thanks! Worked out this was due to rules on our firewall. Previously I'd used an external FQDN for the controller address and some changes to the firewall recently by the looks of it then blocked that access from the server running Spotipo.
Since they are in the same subnet/VLAN I've just changed this to the internal IP in Spotipo which seems to have fixed rather than try and open back up again. Thanks for your help!!!