Nah they don't retest you our bloke said, you just have to get a recent passport photo and attach it to the new form (same deal as you did originally) and send it off with whatever the fee for the actual card is.
Our gas one has a limit but is still goes way hard for a forklift, hit the brakes in the wet and the bastard slides all over the road. We have a second warehouse up the street from our main one, and i'm the only bloke who has a car license AND a forklift license so i am the only one who can drive it up between warehouses. When it hasn't rained for a few days and the clouds open up and give us a shower, enough to just cover the road, it's real dangerous because of how slippery the road is.
Fun times!! LOL.