Went round the block a couple of times, my son driving and me in the passenger seat with VAG COM laptop. Measuring blocks 14 & 15 - one misfire recorded. Is it OK to have the occasional misfire. At what level would cat damage occur? (Fabia 1.2 6V).

if it is missfiring it's almost certainly a failing coil, and it will get worse

Found one plug gap was wider than the others - made it smaller and misfire gone:)