Hi Andy welcome
yes there is a free upgrade for the adventure Island, and it does make raising and lowering the rudder a breeze. I did have to go through my dealer even tho he's in Texas 1500 miles from me now, the kit is very compact and easy to post (mail). the install is pretty easy to,a second pair of hands would have been nice when attaching rudder line to control lines but I managed on my own, I don't have the part #, will try and find and send if other more organised people on the site can't help.
where in the UK are you? I'm originaly a Brummy.