Sadly there seems to be only one or two people in the uk on the reticulum network, I looked on rmap. Given these things have a range of maybe 8km I don't think that for all intents and purposes that it really exists yet.
LoRa can reach hundreds of km's, just depends on positioning. Current verified Meshtastic ground-to-ground distance record is 331km (205mi) which is pretty nuts. Between two mountain peaks, of course. :) https://meshtastic.org/docs/overview/range-tests/
Different countries allow unlicensed use on different frequencies. Look up which is correct for your location.