hey dude, I'm in the UK too and have had a warranty issue with Volkl and Moment. and so I know the position you are in. My advice is get in touch with Line Skis UK first. Chances are if it was your first day out on them, they'll help you out no questions asked really. I mean in general they wont want to warranty skis from the US but, a) you can't get that model in the uk, and b) the case is so clear cut for a warranty i doubt you will have a problem. In my case Volkl Uk were having none of it and Moment didn't have a UK office.
If this fails contact the shop in the US you bought them from by email with pictures and a full story. If you send them this pic then they will most likely warranty them for you without you sending them in. Brand new skis that are broken are the easiest warranty candidates in general. In my Volkl case, untracked.com warrantied the skis for me after Volkl being really reluctant to talk to me in person. Major props to untracked.com and I won't be buying Volkl again because of my experience.
With Moment, I contacted them directly and I did have to send the skis in but then they were legit as hell. Apparently the tech had got the mount wrong and then also messed up the helicoils so even the helicoils pulled out. Despite this Moment were amazing. They sent me a brand new pair of Rockers pre-helicoiled for my bindings and didn't even charge me for shipping them to me, even though the fuck up wasn't theirs. If it comes down to it, get in touch with Line and send them your skis. But just always be clear that its gonna cost you a load to send the skis back in and since the photos make the problem clear then I don't think you will need too.