Windsor dry yeast is a very good option for an English style beer. In my opinion, it is the best dry yeast option for an English bitter, mild or brown ale. It leaves a bit of fruitiness but allows malt character to come through. The other dry yeasts for English styles that I have tried (Nottingham, S-04) attenuate more but are not as flavorful.
Windsor is a decent English ale yeast. It'll be a middling attenuator, leaving behind some body. You'll definitely get some character out of it, as it's known for being a bit estery. Some will get fruitiness out of it, while I get more a yeasty, bread crust thing. If that's what you're looking for, it's a good yeast to use. If you're wanting something clean, look elsewhere, like Nottingham, or the standard US-05.
Just like Peter, I am a fan of Danstar Windsor yeast for beer styles like a Bitter Ale. I ferment warm with this yeast (e.g., 70 degrees F) to accentuate the esters (fruity flavors). As has been mentioned this yeast strain does not attenuate a lot so the resulting beer will have a bit of body. I prefer my Bitter Ales to have some body. I have also used Windsor to ferment an Oatmeal Stout and I enjoyed that batch. Cheers!
