i would like to recomend a good cable supplier and the reasons why
1) you can talk to them very helpfull and will give you the best deal they can and dont mind working with schools
2) very cheap and even cheaper if you are a school ask for a quote if and they will help.
i dont know what postage is like as i picked what i ordered up as they were just down the road.
there website is Cable universe
if you like what you see pm me and i will give you there telephone number you can also email them from the site