aw trips :(
Not sure how much advice I can offer, but I can commiserate. My dd is headed the exact same way. Lazy little sod who only cares about her friends and her social life. The only thing I can do is ride it out and know that one day she will grow up, and try not to take it all too personally. This half term has been a constant battle to get her to do the revision and homework that she should be doing. Every time my back is turned she is giggling with J or trying to dive out of the door.
I was making a roast in the morning, no offer of help. Came in the kitchen, washed her own bowl up and disappeared. J came and did the rest for me. Then in the afternoon she called me, can I get a Subway for dinner. Sod her! The dts have been away so I've been spending time with J, taken him shopping and bought him things, pumpkin carving yesterday, taking him swimming tomo. She is missing out on so much, and now she is grounded because I told her to be home before dark and she disappeared up the high st and rolled in late. So she won't be spending time with her friends neither! 
Her room is a shit hole. We're hoping to move soon to a bigger (4 bed) house. Friends are emigrating and so we are planning to take over their property. When we move she is getting the smallest room again. Originally I wanted her to have a bigger room with a double bed, being older. The idea is that then if my parents wanted to come to stay, she could kip in with one of the others and her room double as a guest room. But the way she treats her room, there is no way I could let anyone else sleep there. So J will be getting the huge bedroom with a spanking new double bed and tv and right next to the second bathroom.
She can be a lazy cow all she wants, but she WILL NOT win through it! And that makes me feel better When she is nice to me, I am nice back. And in the meantime I keep muttering 'And this too shall pass...'
I think even spending the 1:1 time with her only has a limited effect. I mean, I took her on a bloody skiing holiday fgs. I think it helps keep the relationship ticking over, but until she grows up a bit, her friends are def going to be 99% of her world.
And blimey, I went to Brighton when the dts were babies and don't remember it being that strange! I remember cobbled streets and posh shops!
Glad to see Fee is still doing well mama xx
Soks, glad your half term hasn't been all hectic. I daren't even come on to post, as my dts have been away since sat! 
They were supposed to come home tues evening, but wanted to stay longer.