Chicken flies in from Brazil

I've always been partial to a ready-made sandwich from Marks & Spencer, and when I was down at Bluewater in Kent recently, I bought a special "limited edition" chicken, avocado and bacon sandwich. M&S is an organisation that has recently put its environmental credentials clearly into the public domain with its 'Plan A (because there is no Plan B)'. So why the heck do they feel it is acceptable to fly in its chicken from Brazil? I admit that the label on the back of the pack does state "assured chicken from farms in the EU and Brazil", so it's not possible to tell how much of the chicken is sourced from South America. But why, when there must be literally thousands of chicken farms across Europe, is there a need to transport some all the way from Brazil?
I think I'll send them a letter and see how they justify it...