The ants were investigating a discarded sign which helped the photography!
No interactions present.
The shallow angle of the antennal scape joining the head narrows it down to M.ruginodis or M.rubra. I can't tell if the petiole is flat topped (ruginodis) or rounded (rubra). The spines seem rather short so I'd say more likely M.rubra
Lat/Lng: 51.3616, -2.393
OS grid ref: ST727625