Hallo to everyone!!!!

I have a question.. What would happen if I accepted an offer from a University but finally decided not to choose that LLM??

Because it is such a later stage in the process you have to be careful. I have never seen this myself but I have heard that universities can blacklist people in a way creditors blacklist people who do not pay on time.
Your reason has to be credible and verifyable-scholarship at another place, a particular supervisor for your dissertation, decision of your current and future employer on your school, health aspects, etc are all credible reasons. But
You cannot just say-oh, the other school is better than you. The rejected university' reaction will be the one similar to Legal India's when people upset her beloved school.
To answer your other questions-In this case I would probably go to UCL. You would be able to pick up a reasonable number of law modules specific to commodities field at UCL ( and possibly at Kings and Imperial), you might still be allowed
To have a broader appeal to employers I would suggest you specialise not in oil law per say but in project finance law, it I'd broader and covers at least 60/ of work in energy and other commodities.
If you act smart and take a number of well_thought through modules:
1) Project finance law
2) Contract law
3) M @ a law
4) Shipping law
5) Commercial tax law
6) Either fundamentals or islamic law or russian law (depending on which regiona you want to focus)
7) International dispute resolution law
8) Energy law or. Commodities law
You will make yourself very marketable. Considering that you do not have work permit issues and you graduate with good grades
I would say you are as good as hired-and I rarely say that.
UCL will be better for interviews than Aberdeen as most major companies will have offices in London. I suggest you targeting not only law firms and Shells but the likes of Trafigura, I think they will be hiring like mad soon

You need to ask the University itself. At Birmingham, you are not responsible for paying your fees until you actually register (when you enrol). Therefore, you can withdraw your acceptance before then without any consequences. I don't know whether it is the same at other Universities.

The issue is not only fees. By offering you a place and after
receicing your acceptance a university by law cannot offer
it to someone else. If you cancel your acceptance in May,
a university has time to offer the same place to another

candidate or adjust their budgets accordingly (for the
number of teachers they need, IT equipment, books in the
library etc). If you cancel your place late in the day, the university
cannot offer the place to another candidate-too late, or
make budget adjustments..now think if a course has 200
Students and they also cancel and went elsewhere, the university will still
Have to pay yearly salaries to staff otherwise they sue them. This will result in losses
For universities, which are alreadily poorly funded
That's why if your reason is serious and VERIFYABLE, a university will be OK. If not-they
Can cause you problems out of annoyance. But would not you do the same?
The university my ask you to pay the fine...this is in their right

Well I don't know what Universities you are talking about, but I can only talk about Birmingham as I said. I asked them if I could cancel after acceptance, and they said yes, if it is before I register. I asked if there would be any fines or fees to pay etc, and they said no, and didn't mention anything about making things difficult if I go elsewhere. What exactly can they do anyway, if you've already accepted another offer elsewhere? I can't see the other University withdrawing your place at their say so...

The obvious and sensible thing to do would be to simply ask the University in question and see what they say.

Thank you very much for your help.
As a matter of fact I think that I am closer to UCL but I have some second thoughts.
Thanks for everything. I wil let you know of my finai decision.