I want take my block of Six static public IP's with me to the FTTP isp !
As others have said, you can't, unless you buy your FTTP service from the same ISP as the ADSL2, and they agree to transfer your block of addresses over to the FTTP line.
On residential services the best you're likely to get these days is a single static IPv4 address plus a block of IPv6 addresses. Even then, many residential providers have dropped the option for static addresses (e.g. Plusnet)
You could rent a new block from your provider, and renumber your servers to the new addresses, but there are very few providers who offer blocks of addresses, primarily business providers. It's also quite common to pay an extra £2-£4 per month *per address*
Someone mentioned AAISP as an option. You could instead use the AAISP L2TP service, which lets you tunnel AAISP's IP addresses over a different provider. It cost £10 per month last time I looked, and has some limits on the speed and data volume transferred - although if you're used to ADSL2 then those may not be an issue.
However, my recommendation is to reconfigure your network to run on a single static IP address, which is what I've done. The details depend on exactly what services you want to run.
A simple approach if you are mainly running web services is to run Pangolin (the Fossorial stack). In fact, you don't even need a single public IP address, as long as you run Pangolin on a VPS which has one. It sets up encrypted wireguard tunnels between each of your servers to the Pangolin server, which accepts inbound connections, authenticates them, and forwards them to the appropriate server.
Otherwise, the general approach is that you run all your services on private IPv4 addresses and/or public IPv6 addresses, and then port-forward incoming connections from your router's one public IPv4 address to the relevant server(s). For example:
* Port-forward E-mail ports to your mail server (TCP 25, 110, 143, 465, 587, 993, 995)
* Port-forward 80 and 443 to a web reverse proxy. If you use something like sniproxy or haproxy which can do SNI sniffing, you can forward SSL connections to the correct backend server without decrypting the traffic and without needing its own certificate(s) for the domain(s) you use.
If you get a block of IPv6 addresses from your provider, then publish an AAAA record pointing directly at the target server, and an A record pointing at the proxy. Then any IPv6-capable clients can directly talk to your servers, and any IPv4-only clients will transparently go through the proxy.