We've had a server at Bytemark for many years (since the summer of 2009). For the most part they've been good, Towards the end of last year, they started charging for extra IPv4 addresses. This came as no great surprise, given the near-exhaustion of this finite resource, but our modest /27 suddenly represented a 1/3 increase in the cost of our server.
Fortunately, Bytemark agreed to waive the increase until our next annual renewal, after I got a bit shirty about mid-term price increases. Which left us with the joy of consolidating our usage. They're quite right to point out that the advent of SNI support in all modern browsers, and things like sslh mean we don't need so many addresses any more, but having parcelled them out to my six users in blocks of 4 (making firewalling easier as everyone had a /30), I had a long and tedious consolidation exercise to carry out.
Happily, many reboots and much faffing later, we're nearly there and should be able to hand back 16 addresses of our 32 next month, thus cutting our cost by £192+VAT/year.
This has prompted me to take a closer look at going all-IPv6. I've ordered a small IPv6 only VM from Mythic Beasts to play with. Teething troubles aside, it works quite well, with inbound proxying for the websites and NAT64 for outbound access to IPv4 services. Running just the one IP stack feels much cleaner and easier to administer, and opens up the possibility of using an IP address per website/service with no danger of running out.
Edit: Bytemark's original announcement failed to mention that it's £1 plus VAT for each IPv4 address. Sigh.