The _lines_ x 3 cost about £90 per month in total, including £30 for BTW Premium prioritisation, and then there's the cost of data inbound on top of that, which varies a bit.
I have two EE basestations in reach, good signal because I am so high up, while neighbours down nearer the shore ha almost nothing, SMS only if they're really really lucky, and have to drive up the hill for the most part to get incoming messages.