Where can you find the cheapest plane tickets online from PHI to an airport near derby,derbyshire,england?

I want t go visit a really good friend of mine, i live in the states and she well obviously lives in derby. i'm on a Very tight budget right now though i dont plan on going untill next june or july if its possible that there is a website out there that offers plane tickets under $1000 with the fees included in there it would be awesome!!! thank you to whoever answers this!