Hi Mark,
Very few clubs run a Biland grid. There is a Biland series which tours around various tracks around the country but it isn't for beginners. Information about the Biland series can be found on the Saxon Motorsport website:
http://www.saxon-motorsport.co.uk/
Having said that it doesn't mean that you've bought "the wrong kart", use it as it is to learn how to drive/race and when you're ready to have a go at the ARKS -*test*-('") then you can decide which class you want to join/buy-into.
As for the gearbox classes, Llandow did have a ICC-125 class but it regularly pulled only 3 drivers, Dan, Byorn and Chris, so it sort of died. I'm sure they'll be keen to hear there's interest in the class, but I'm not sure (again) whether this is a good class to start in.
Stick to the Biland for now and learn the kart/track and make the decisions later. You'll be more than likely going out with the Snr Max karts the Biland being a bit faster than them.
Dan