Thanks Brendan
I found this site which I thought is good value.
http://www.berndmargotte.com/technic..._power_en.html
This guy simply powers a camera with a 7808 without heat sinks or caps.
Even if I take the advice you and others have posted, I am still interested in knowing why there is so much variation in the cap values used with a 78xx voltage regulators - particularly when drawing power from similar sources.
Cheers
Doug