The owner of api.superfastmaps.co.uk has configured their web site improperly. To protect your information from being stolen, Firefox has not connected to this web site.
Its ok, I found out why its broken.
Their SSL Cert has expired today
Protocol: TLS 1.2
Key Exchange: ECDHE_RSA
Cipher Suite: AES_128_GCM
Valid From: Wed, 17 Jun 2015 23:01:10 GMT
Valid Until: Tue, 19 Jul 2016 03:40:24 GMT
Issuer: GeoTrust DV SSL CA - G4
SCTs: 0 SCTs
I have just reported it to openreach, like I did last year, they really need to keep an eye on this kind of thing LOL.