also have to pay an import duty on it, up to 13% of the value I think, depending on how big the engine is
I think you may not be quite right here as we don't have import duties within the EU.
I have European insurance and need to drive it back to the UK once a year for MOT and tax disc.
But can you legally drive it in Poland? I'm not keen to register my car in Poland at all, it's just that I'd probably have
to do it to use it here if I stay for more than 183 days during a year.
And no, the car's not RHD.