Chris, I paid $100 US for my 1978K. It had 4K miles on the Speedo. It had also been put away "as is" in a dry basement for 18 years. The tank and carbs were filled with what was at one time Gasoline(Petrol), and the brake system was filled with something like chrystalized honey. The paint and chrome were totally mint, and the motor not siezed. I suggest that you do what I do which is a rolling restoration. I am slowly replacing the rubber parts and other pieces which simply degrade with age. I like the BattleAXxe tires. They look Retro enough to match the bike, and they are modern in their handling. They track straight on most road surfaces, and you can lean that baby over till the sparks fly off the pegs. Make it safe, ride it well and improve it as you get a few extra quid.
Bob