Thanks @MrWill. In the first six months it has had a new alloy rad, new alloy fuel tank (including a one way valve, otherwise fuel spills out of the filler!), CV driveshafts, LED exterior lighting, tyres and a stainless exhaust - so loads of invisible stuff. Next is a new roof, which won't be cheap, and a new dash to replace the homemade one. As the dash is coming out then I may as well rewire it too.
You never really own an old Lotus, you just keep restoring it for the next owner!