1. Also, the technology used to initiate the time bubble itself was probably in Toshiko's computer, and that is the desk nearest to the water tower.

2. Ianto is apparently incredibly thick and wouldn't consider Gwen getting out, taking protection other than a hand gun to meet an alien race, or a gas mask to protect him from the biological warfare that said alien race has already threatened to employ once before.

3. Gwen is magical and was bred with superhuman powers - like the ability to run about every day in heeled boots. Either that, or a wizard did it.