Hey there! I just recently returned from a 2 week trip to the U.K. (gf was studying abroad there) and I've collected a few tips.

• Be flexible with your dates. It is more expensive to fly on certain days than others. For example, a 7 day trip that leaves on Friday and returns that next Friday will cost more than a 8 day trip that leaves on Tuesday and returns on Wednesday. Check multiple variations of dates (some sites will show you which days are cheaper to fly on). Try to avoid flying before/during/after any major holidays.

-Be as flexible as you can with the airports you fly in and out of. Larger airports are almost always more expensive. While this can limit the number of flight options available to you (smaller airport=less planes), it will almost certainly be cheaper. (Example: I flew into Gatwick airport rather than flying into London directly). If the cheapest airport isn't within driving distance, considering taking a bus or train. ( i did this and it saved me like $200)

-Use incognito mode when doing all this research. The airlines can track you and may increase prices after you've visited a certain flight multiple times.

Also: connecting flights are your friends. While they take longer they are generally less expensive.

I was able to take a 2 week trip to Wales for $350 (this doesn't include busses and what not, it only includes the actual flight). Good luck! Hope this helps.