Which version of certbot are you using?
certbot --version
Getting certbot-auto may help. see: Migration to new server and also apache to nginx - #4 by MitchellK
external access disagrees:
openssl s_client -connect www.stoke-fest.co.uk:443
CONNECTED(000000FC)
write:errno=0
--
no peer certificate available
--
No client certificate CA names sent
--
SSL handshake has read 0 bytes and written 176 bytes
Verification: OK
--
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
SSL-Session:
Protocol : TLSv1.2
Cipher : 0000
Session-ID:
Session-ID-ctx:
Master-Key:
PSK identity: None
PSK identity hint: None
SRP username: None
Start Time: 1506275444
Timeout : 7200 (sec)
Verify return code: 0 (ok)
Extended master secret: no