PlusNet offer a static IP address for a one-off fee of £5
Been with PlusNet for a couple of years on their fibre option.
I work a lot from home and use a site-to-site VPN with the office.
BT wanted me to go "business class" to get a static IP.
Plusnet were happy to provide me with one for a one-off fee of £5.
Generally pretty happy with the service.