I think I’ve narrowed it down to the cleat rubbing on the plastic plate in the centre of the pedal.

Any fixes? Or is a good reason to upgrade…

Mine and all my mates do it. I greased my axles (ooh err) as they were dry (as did all my mates) and it stopped. Fella I work with has just bought some new ones, 3 weeks in they are creaking. I’ve had no dramas with my 105s

Spray gt85 on the cleat and let it dry. Do the same with the pedal and if that’s the cause of the creak then sorted. But I would also open them up and pack them with a good thick bearing grease. Should be silent as a lamb.