It's always going to be hard when you encounter non Brits in jobs with British companies as described in your post. It doesn't officially class as racism; presumably these pilots have UK or JAA licences, together with the necessary experience.
However it should begin to cause concern if non british pilots are being employed for lower financial rewards than British Nationals would accept. In this case, it is unlikely to be the situation. However it doesn't mean it doesn't go on. More to the point, it doesn't mean it won't go on in the future. That's the possible eventuality you you should worry about.