Just a follow up to this.

So I never ended up contacting O2 to say “please stop this”, I just used Wireguard to home and ignored it. Until the local Morrison’s wifi started doing the same thing but worse and I couldn’t event Wireguard round it.

So I finally just bought a domain and setup my Apache to redirect the old duckdns to the new domain.

So far this all seams to be working great.