This may be the common rustic (Mesapamea secalis) and it is, indeed, a widespread and common species from June right through until October but you are unlikely to see it! The reason may be obvious when you look my photograph and see that you chances of finding it in the day time are very slim as it is so well camouflaged that it can rest on a tree trunk or in scrub and you would never know it was there. It is attracted to light so you may see it at rest on your window.
The colouration of this species can vary considerably from pale brown through to almost black but the rusty colour seems to be the one I have most often in my moth trap. What ever the main colour of the fore-wing the wight mark and the white dots on the curved wing edge are always quite clear.
There are actually three species, the common rustic, lesser common rustic and Remm's rustic which are indistinguishable without the use of magnification and, as regular readers of my nature notes know, taking specimens and looking in that degreee of detail is something I do not do so let us just accept that this is probably what I say it is as it is the most common of the three and if it is not then we will never know.
The larvae feed on grasses and overwinter as a pupa.