The deadline for courses such as medicine/dentistry or applications to Oxbridge is 15th October at 6pm. So that may be a reason why some have already received offers. For the rest of the courses the deadline is in January sometime.
I heard that unis are already giving out offers now, i'm asking if it matters to get your UCAS in before the deadline in January like are some unis first come first served with their offers?
Tbh, even though they're not supposed to favour applicants who apply early, offers are usually made on a 'rolling' basis. If you've applied when they still have 50 places, you're more likely to be accepted than if in Jan they only have 5 - they have to be more selective. The odds are better for applying early, but don't rush if you're not ready, you don't want to make any mistakes in uni choices
For some unis and courses, i.e. History at York, they refuse to look at applications until January due to how competitive it is, but a lot of the time they'll send out offers as soon as applications come.
It's pretty straightforward, the earlier you are, the less competition you have. I would still class anything before mid-November as an early application though so don't rush yourself.