When you do the valve check, look for worn buckets (lifters) as well. My 88 had a couple buckets worn that would rock in the cam towers and clatter. Sounded exactly like a valve tick, but the valves were in spec. Just like a piston, the buckets have skirts, and they are pretty thin. My skirts were a smaller diameter than the crown of the buckets, making them rock. We will call that bucket slap... A new set of buckets from JAE and my tick disappeared. At such low mileage though chances are it is just a valve out of spec. Not too hard to check the valves, total PITA to adjust them.
1988 Lotus Esprit Turbo
2002 Lotus Esprit V8 25th Anniversary #008