Well, it depends a little on which English yeast it is, but in general, you're going to get more esters from English yeast, and lower attenuation. You can tweak things, of course--for example, English yeast tends to be highly flocculent, which is part of why it attenuates less than American yeasts, so you can rouse the yeast (gently rock the carboy to stir up the sediment) to keep the yeast in suspension and keep it fermenting. As for esters, you can control those in part by keeping fermentation cool.
But I guess the real question is style. Do you want to make something that is a little fruitier and maybe maltier than an American yeast would produce? Those characteristics seem to go well with barley wine. So I think you're probably fine using whatever this English yeast is.
The one thing you might need to do is monitor the fermentation. If you get stuck at a gravity that is higher than you wanted (a possible risk of using less attenuative yeast in a big beer), you might need to pitch a different yeast later. So, e.g., ferment with an English yeast for a week, then pitch US-05 or something else to get the last bit of attenuation.
I guess in sum, it just depends on what you want to do. But there's no per se reason you can't pitch onto the English yeast.