I called up Hyperoptic and they told me this is a common problem and that the public IP address may have been blocked and I have to call up British Airways to request that they allow a connection from it. I think it is ridiculous that it is the customer's responsibility to contact a website provider to allow a connection through when it the service provider's responsibility to provide the internet connection!
The only other solution I was provided was to pay £5 a month for a static IP. It seems completely unreasonable that I have to pay extra in order to get what should ordinarily be provided as part of the service. Even Sky provided better customer service than this! I am seriously considering going back to my Sky Pro ADSL connection because even though it's slower, at least it works.
Edited by binary0110 (Sun 11-Jun-17 12:49:25)