You're screwed.
You can try pleading to the network admins for your Uni, but i wouldn't expect much.
Start downloading something over http, see if the speed drops on that after 5 mins. I'm thinking what they've done is put in a system that lowers the priority of TCP connections that persist beyond 300 seconds - a modest hit during file transfers but a real killer when you're using packets with small payloads. If you're lucky they won't have enabled this if you're connecting to port 80 (If your download stays at a constant speed this is the case).
If that's the case give
www.your-freedom.net a go, it's free for a 64k connection that should suffice to play TF2.
I had the same problem as you with WoW when i was in Uni accomodation, and your-freedom fixed it (I actually paid for the unlimited service, and got outside ports tunneled through so i could host my own web server with 10Mb upload and use an active connection for direct connect/torrents etc