Well, several years back, when I was going through a financial issue, I actually took them into a shop to sell. Unfortunately, the guy was like "I can only give you like $200 for all the boxes."
The reason being is that most of the comics are from the late 80's, early 90's when comics were booming and they were printing off millions of them. Then, he said, Gen X grew up and were selling them off so the back-issue market is flooded with the exact same issues I have.
But what I plan on doing is going through them and picking out the issues I KNOW are worth more and holding onto those. But I'm curious if US versions of comics have any more value in the UK or not (much like CD shops charge more for Import CDs). Something I'll have to look into.