Belgian Style

[JayBee]

Saw this on an Aussie site and thought it sounded interesting although I couldnt contact the guy to find out the OG and FG.
1 can of Coopers Blonde
500 grms light Spraymalt
1 kg Belgian Candy Sugar
300 grms Brewing Sugar
Belgian Ale Yeast
30 grms Tettnanger hops

It looks quite easy to do although I never found out which particular yeast he used. Tettnanger hops don`t seem to be the most common either so I was wondering if Saaz would be as good. How do I find out what the OG and FG would be if I made the brew up to around 20-21 litres? Iguess theres a simple formula somewhere that I need, especially when I move away from just doing kits and additions.
Any thoughts?