As the saying goes you get what you pay for, and as the previous post states a good second hand gun is the best idea for a new starter. You can pick up a good over under with multi chokes and ejectors for under £500 look at lanber's, Bettinsoli and miroku's all good value.
My AYA was in great nick when i bought it for <£400 and it came with all the chokes. Good solid gun, great for rough shooting and breaking clay.