Garden Warbler?

Could I have seen a garden warbler in my garden several times in the past week? It is about 14cm long, and has no trace of yellow or green on it. Paler underneath than on top, and no distinguishing features. It looks exactly as it should in the book, apart from the fact that it shouldn't be here at this time of year. I am on the coast in Sussex. 

Very grateful for any suggestions. Amaretto