Hi Buzzawak
Cheers for the input and answers. I got the bike a while ago as a non runner. Its not had much done to it - new wiring loom, CDI, Carb strip, service and tarting up. Its only got 9000 miles on the clock and I'm led to believe was one of the last RRSP's imported in so I feel honour bound to try to restore it to former glory.
Yep, I'm using coolant. Theres been a lot of good suggestions/advice from the forum which I will act upon later this week. I've just started a new gym routine/diet which doesn't mix well with being in small shed like spaces!

I don't understand!!!!! Before I put the rad back on, I wire brushed/cleaned all the metal hose attachment points and made sure everything was nice and tight. The little f***er worked perfectly - the fan kicked in earlier than normal and there was no bubbling in the expansion tank. I repeated this 3 times. YES!!!!
No.
Took her out and it was great - even the performance felt better. The temp gauge didn't even reach half way. Next day, after giving her a good workout for 20 minutes I stopped for a gasper. Nothing coming out of the breather tube, no noise from the expansion tank. All good.
On the way home everything was fine until I got stuck in traffic and the temp needle decided to go for it, the fan kicked in but by the time I'd parked up the expansion tank was boiling like a good 'un. Bugger.
Its going in the shed (going to strip/balance carbs and change fuel filter cos its really hard to re start when warm and also tends to die at idle when warm - not fun at traffic lights) so I'll make a start on everybodies suggestions.