srw
It's a bit more complicated than that...
In those circumstances you're right.I'm a contractor employed by a third party, so I don't want to play fast and loose with their rules. If I was an employee it might be different. It seems my only option would be to buy a cheap clunker and an expensive lock and use the lamppost outside option. Which, given that I don't much like cycling in town isn't going to happen.
But especially if you're in the same office for a few weeks you may well build up enough of a relationship with some members of staff who would really like to ride to make them aware that their situation is not normal. It's the sort of thing that people discuss over a beer after work.