I've taken you're advice and bought a trackball.
I'll let you know how I get on.
I'm only 33, but I feel like I'm dropping to bits ! Ha ha.
Thanks very much to everyone who's responded, and for all the help and advice.
Hi - on the software side of things I have come across the following:
I saw article on this in Lifehacker a year or two back and in googling it nearly every second article seems to mention it for RSI in combination with PC's.
I personally had a lot of trouble with RSI because of my work at the keyboard all day long and then at home for half the night. What my main help was to introduce the Microsoft Ergonomic keyboard plus the then excellent Logitech Trackball which was a large one with the ball being almost exact same size as a Billiard Ball. I still use it from time to time if I find myself getting tired in the wrist area. The other thing that I added to this though at the time to overcome the problems was the use of a "Thermoskin" brace for my wrist. The beauty of it over the normal wrist braces is that it has a steel insert which follows the inside contours of the hand wrist brilliantly and works a dream with the Trackball.
So if you don't get any luck with anything else I would definitely recommend the Thermoskin brace from your local Chemist - currently they sell for around $25 to $30 here in Perth, Western Australia.
If you would like a picture of the brace I am talking about drop me a line at firstname.lastname@example.org
and I will forward it to you.
Sorry if I have gone on a bit but I know how it is with RSI, it can feel miserable and very very painful.