I find that the best way to identify tall fescue (Festuca arundinacea) is to initially look for a tall grass! That may seem obvious and it is but this species is tall, very tall, growing to six feet high which is, yes, tall for a grass. This is its stand out feature. Once you have a grass as tall as you are then just check that it is growing in a tussock, that is, a cluster of stem originating from a central basal point (in the States this is know as a bunchgrass). From there it is pretty easy to check the leaves and the florescence just to be certain.
This is a species of open grasslands but it is most often found on roadside verges where it is not uncommon but with our zealous verge cutting regimes you may not actually find it that often! It is the basis of several cultivated species that are used as forage crops as well as ornamental grasses for gardens. In its wild state it can pose problems for livestock because it frequently forms an association with a friendly fungus and that brings about chemical reactions that produce alkaline fluids in the stem. This is a complex area and is explained on Wikipedia if you really want to know more: https://en.wikipedia.org/wiki/Festuca_arundinacea