can work fire me for calling in sick when im not actually sick?

yes they can fire you.

Yes. You should have told your boss in advance, so they could work around you're not being there.

I doubt you are contracted. And it sounds like you already tried to get the weekend off. So figure you'll be fired. Hope it's worth it, because now you'll have trouble getting another job. When they call your boss I doubt he will give you a good referral.

If they find out you're lying then yeah they could sack you.

If you've asked for the weekend off and they say no and then you phone in sick they're going to know you're lying. Some firms might also phone your house and check or even come round if they're suspicious of you.

yes they can easily fire you for faking. They don't have time for people pretending to be sick and just hire someone more productive. But if you are bounded well with the boss, like friends, then he well probably just make you work late :)

Yes, specially if you were silly enough to friend either your boss or a grassy workmate on facebook but you'll probably just get a warning if it's the first time.

Your employer refused to let you have time off because they couldn't spare you. If you already had plans, you needed to state this at interview. Not only will you let your colleagues down as if you do not turn up their plans will go to pot because they are covering you, but you will be hauled up for Gross Misconduct, which is what not turning up intentionally is. I seriously hope you get sacked and dont get a reference, and are proud of taking a job someone else would have jumped at.

They won't unless they find out but even then, there is a slim chance of being fired. Just tell your boss you need a few days off before hand and then see what he can do for you. Do that or ask your trade union for help.

They certainly can and probably will.