Man I'm paying £100 for 2!
£28.99 for Zen 80/20 (excluding line rental), £10 Voxi (deal for people on low income for six months), £17 for Three (just one of their random 12 month deals).
I did buy the routers outright so I could go for SIM-only/PAYG packages.
I did forget line rental as that's with BT Basic at £5.16/month and AAISP L2TP at £9.20/month.
Will move landline to AAISP VoIP which will drop that to £1.20, not decided on the L2TP service yet as its not been especially stable over 5G and pfSense has a nasty habit of not bringing it back up when it drops, which kinda negates the point of having it as a backup into my LAN if the main WAN goes down.
What would be ideal is if a CityFibre ISP offered a really basic, cheap, package for VoIP backup purposes. The catch is I need a static IP on it so I can also keep my XMPP server connectivity, as you cannot do DDNS to a subdomain that has more than one IP on it (at least on Cloudflare).