Plans to apply for UK - help!

Hello nurses. You might have heard too many about this thing but i need more pieces of advice regarding applying for a student-work visa in UK. Had my video interview done yesterday and paid 20 thou. But I still have one week left to decide and if i back out, they will give back the money. The agency said to expect a call next week from the manila office for our payment for the tuition (300thou). I have read threads regarding this one just now and have realized the sudden increase of tuition fees. My agency is International Student Advisors Inc (ISA). During the orientation, the bristish representative, who also interviewed me, said that we can stay up to 4 years but he is not sure what will happen on the 5th year, he was being frank on that one though. The agency said that the total amount that we have to pay is more or less 600 thou including the tuition of 300. The rest is for the processing fees, airfare, accomodation and etc. Please advise me on this one. Thank you.