Cant work out problem with Octavia Scout MK2 TDI. Intermittent Blue Smoke only when engine warm.

I am at a loss to figure this out.

My lovely 2011 Octavia Scout 1.6 TDI (220k on odometer) has started blowing intermittent blue-grey smoke when warm and under power, usually for a second or two, then it clears.

The car is running beautifully, regular checks show it doesn't use oil(have never needed to top it up between oil changes), there has been no coolant loss or discolouration , no power loss and no turbo noise.

No smoke on cold start, but after a long trip the next day, it blows intermittent smoke on acceleration when the engine is warm.

No error codes or warning lights...

Cold Engine test shows no blue smoke

A little oil in the crankcase ventilation hoses.

I'm thinking valve seals, but if anyone has any other ideas, I would love to hear them!

Thanks in advance for your advice. I love this car, but if valve seals are gone, then it's curtains.

Baz