Yes, all venues have secure places to store bikes.  However, you are responsible for your own property whilst at the courts.
At our Angel venue bikes can be left next to the courts, but may not be taken inside the court fence.  In Highbury no bikes are permitted inside the school property, but if you ask the receptionist for the key, then you can leave your bike in secure storage just outside the school. In Dulwich there is a bike rack directly opposite the main reception.