Thanks to all for the suggestions
The unit with the cross-hairs or "rifle sight" is optimum for CAD, but as it resembles a mouse in many ways, I can't see it being suitable for my RSI.
I should have bought the thing this week, but I haven't and I'm now leaning towards the Intuos A5 unit.
Rip-off Britain being what it is, I've noticed you can get Wacoms on Ebay for the same amount of dollars as you pay here in pounds... Hmmm...
I have friends who work at educational establishments, and feel tempted to ask them to buy with Wacom's educational discount... I probably won't as it's a bit naughty really
Anyway, I might as well get the A5 with pen I think.
Cheers!