Oh honey, big hugs. I feel like you're in the eye of the storm so can't see what's going on.
And that's because they have been emotionally manipulating you, and degrading you, I'll bet it started small and has gradually gradually become worse and worse.
As everyone else has said, they are not you're friends, they are actually quite evil and are using you for some sick twisted entertainment .
They are making you feel small so they can feel big - it's all they've got.
It's not a reflection on you, it's a reflection on them.
They are never going to reimburse you so ring the hotel and either cancel or explain and tell them not to let them check in - then go by yourself.
Manchester is so fab, I bet there are some great things to do there maybe there are Meet Up group events going on?
Then let them turn up at 7am, and not answer the door, sleep in, do what you had planned and catch the train, travel first class.
Breaks my heart that people can behave so cruelly, but some mean girls never grow up - they just grow old.
No-one deserves this.