Silicone spray as a release agent? I've just printed my very first part and it did not want to come loose from the build plate, it fact, it just broke instead.

I can heat the bed up again and work it off, but I wondered if a release agent would be better?

I have a silicon release spray (like those use with molds).  Could I spray the base with that before starting printing?
The problem with using a release agent is, you really run the risk of the print not sticking to the bed at all. Sticking to the bed is uber important, because if it's not there, the piece isn't going to come out right. Having it stick to the bed is a good thing (something which I struggled with for a while!!). 

I believe what most people do to get the piece unstuck from the bed is to use a putty knife. Wedge the flat part under the piece and twist slightly. Continue doing this around the print until you can get it to release. Your best bet is being careful by going easy with it though. Also, if the print is sticking well to the bed, ensure you're not using a raft. This will make it even more difficult.