Your 15 mate, just get the train with some mates to MK, Tam or even Hemmel. Get some boots fitted then go ski the park for a few hours to test them out.
What people here forget is that a boot, itself is only the starting point, you need footbeds, possibly alignment, boot stretching, liner work ect ect. You don't get any of that online, that's why the boots cost less. Buy in a shop its much cheaper in the long run, as once you buy them you should not have to pay any extra for follow up fitting, and you will know its the correct boot for you.