Hi Zoe,
This is normally the case with wireless networks - sadly.
Can you confirm that your flatmates are experiencing the same problem.
We need to know as, if they are, then it is obviously a router problem.
use this test please - wait for "Begin Test" to appear
http://www.speedtest.net/
Let us know the results.
It would be helpful to know the results from upstairs / downstairs / and one or two of your flatmates.
It would also be helpful to know what connection speed you should be getting - in other words .....what package is being paid for?
Is this network "Secured" ?
If it has a Network Key ( password ) that is needed to initially connect then this is extremely unlikely.