About 10 minutes later the cleaner knocked on the door and asked if we should be evacuating as the fire alarms in E (east) and N (north) towers were sounding. The answer to that is no - we're on a zone system and T block is on a seperate zone.
I joined some other technicians who are fire wardens (I'm going to be trained as one at some point) and assisted them. There was a lot of steam/smoke coming from a ground level grate and a 'funny' smell. Fire service arrived and went into the maze of tunnels below the site (heating/electricity/cables etc). The Atrium was evacuated next due to the fact that the problem tunnel was below it.
In the end the smoke/steam was blown out of the area and everything checked by the fire service - no fire but a 4" hot water pipe had burst and the electrical trips went, cutting off the power to a few things including some fire alarm circuits - hence the alarms went off. The entire university has no heating until a repair is made (the pipe is part of the heating system) and there will be no heating to T block (my base block) for the 'foreseeable future'.
Funny thing is - I wonder if the plumber trying to repair the heating in the few rooms in T block had caused the main to burst (or it could have been the cold as I had spent a while clearing the windows of my car off so I could drive to work.