Don`t know about discounts and I`ve looked at all the main ISP`s in the last week. I`m surprised the landlord hasn`t set up the BB already since obviously he has the necessary BT Line installed. I would suggest that you look for an ISP who provides a monthly contract and not a minimum of 12/18 months - holiday periods during the summer could save a straight 2 months - Look at PlusNet and Virgin for these.
Also with 5 students all using the system you`d have to be mindful if one abused the fair use policies in force which could cause a "throttle back" on the service. Although you can get a £14.99 a month service from both the aforenamed I would suggest they prepare for a truly unlimited download tariff at about £25-30 with at least 2MB speeds.