Recently had a few occassions where some puffs of blue tinted smoke have appeared on tick over. My local friends at AP have made an initial guess at possibly valve stems (same as you Andy).
Funnily enough, the owners son has also told me he wants to buy the car and has offered a reasonable price. And he is even happy to buy it if the engine goes bang, as he would rebuild it stronger from scratch but of course pay me a lot less for the car.
Maybe it's time to sell up while I have a reasonable offer for her ?