MDJP85

I have recently started having issues with my car juddering when going into gear. It seems to be getting worse. It's done less than 30k miles so would be surprised if it's gear box related, but you never know. It's started happening after a service and new tyres being fitted. I've noticed two things: A diagnostic error of P2B5E (seems to be coolant related https://www.mycarly.com/obd-codes/p2b5e-engine-coolant-flow-control-valve-position-sensor-circuit-low/) The coolant in the reservoir is filled way over max. It's essentially undrivable and being an automatic so many garages don't think they can help. Appreciate any thoughts people might have. PS are all the skoda error codes available somewhere?