Anyone ever done a Category G test?

[mat777]

Now that I'm 21 (well, in a few days!) I'm thinking of adding a class G to my driving licence seeing as I spend so much time around traction engines and therefore steamrollers - I figure it would be a useful thing to have. Information seems to be scant on the web though, apart from age limits etc. The only sites I can find are ones advertising an all inclusive 2-day course type affair for hundred and hundreds of pounds - there doesnt seem to be anything from the DSA on where my nearest centre would be, for example - just that "specialist vehicle" tests cost £62.

Is the test itself hard? Does it really require a 2-day intensive course, or could someone with experience of engine driving rock up on the day after a few hours practice on a steam or diesel roller and have a reasonable chance of success?

Also, it says I need a provisional G entitlement on my licence, but I only have f,k,p on the back of mine under the full classes. How do I get it?

Thanks,

Matt