Fundraising ideas? Need to raise £3,890?

[Faketannn]

Hello
So basically there is this trip to Ecuador , South America during the summer of 2014.
Its a summer camp where you go for a month, and stay in a tent (Not at all luxurious) but its to help build schools and the community. We help teach little children English and just do a lot of things that will benefit the community up there. We also get to visit the Amazon rain-forest and go Scuba diving.
I have about a year and a half to raise the money, but i have no idea how i'm going to do it!
There's only so much cake sales will make lol
i'm only 17 so i don't have money to pay for it myself..
We can also get people to sponsor us but i don't know who i could go to..
I'd really like to go, its worth 70 UCAS point and it will be during my summer holiday.
I live in wales and i think its going to be loads of school going together, obviously not everyone who wants to go will be able to but id really love to give it a shot! i've always wanted to help people around the world and this would be such great experience!
Do you have any idea on how i can raise the money? it works out at about £50 a week.
Ok thanks everyone!
i know its expensive but its for the travel, food , scuba diving and probably healthcare