Hello
I was in south england myself in 2006, but I can´t said you if your locality they live

I went into South Devon, Torquay...
But now seriously... Myrmica rubra preffer open and also forrest country with mixed foliaceous trees.... They like a bit wet localities, cause humidity in the ground which´s near their nest is usually around 70%.... Colonies have ground and underground nesting, but the best thing is, that the queens are restraining nearly surface, so you can find them easy.... These red ants like to make their nest under old woods, which are laying on the surface. They also like objects like old bricks, old leaves... When you remove some of these object sidelong, you usually can see a lot of workers and more queens....
Their colonies have usually about 300 workers and more than 20 queens, but it´s about their habit...... Colonies are behaving like superorganisms and they usually have few smaller colonies, which are comunicating with their mother colonies by some kind of ways... I don´t know much about these ants, this things wrote up are by my own experience. I think here are people which can give you more, better informations...

And sorry from my bad english