Thank you so much, Hover Bovver !
Your comprehensive and clear reply is yet another illustration of the quality of this great forum and its people. I think I will go for the 495.
And now the revelation: only after I had sent my message, I realised I had done so in the Heli forum. This is because I had found the GPS thread via the "search" function. I am just a PPL(A) with no rotor experience whatsoever - an intruder in this section (!). But thanks for your answer anyway.
Good landings (or should I say "good stationaries" ?),
L