I think it is. The Essex skipper has a black or dark brown end to the antenna (as does this specimen) while the small skipper, with which it can be confused, has an orange tip. The only other reliable method of distinguishing these is by the sex brand and that is only in the male and requires a view of the upper wing.
Thanks for your reply. I have a number of photo's of skipper butterflies and cannot say for certain any of them are essex , this particular one as you have said does seem to have dark antenna, that is what made me think it could be a essex , unfortunately was unable to get any more images of this particular one.
I think the field guides place too much emphasis on the colour difference being on the UNDERSIDE of the antenna tip. You don't have to photograph from below to be able to see this. Here's a small skipper I photographed last year and the colour can be clearly seen despite the downward angle of the shot.
PS Very odd things happening here. I look at this image on the website and the orange tip is not clear. So I opened this post to make this edit and the photo in the edit window once again has a clear view of the orange tip. I hope you can see it when you look at this post. (To get the original colour, click on the photo even though it will be the same size the original colours will be clearer.)