im after 1 of these things that sits in the fins of the rad. and it wired to the fan, there is a dial/switch which allows you to adjust the temp. at which the fan kicks in.

what are these called and where can i get 1?

ta.

 

Edit, sorry just read the question properly, this is a in water one, I've seen the ones you mention, so will do some digging for you!!
These type you describe are made by KENLOWE, may be made by others also, I don't know, but Kenlowe certainly do them, called adjustable automatic fan control, with a range of 55C to 120C adjustability they have a 3C hysterisis(range), can remember my dad fitted one in 1980 to his car, still have that same one today and still works perfect, though car rusted away!!
www.kenlowe.com/fans/consumers/fans05.html
tabetha