Is your car chugging during normal driving/operation? Mine only does it for 2-3 seconds, when it's restarted after already being warmed up. Normal driving is fine, idle is smooth, and performance is generally strong.

With regards to parts... I haven't bought many myself, but have used Autodoc and AwesomeGTI in the past. Both recommended. Autodoc is often cheaper that garages quote for parts, but takes 2-3 weeks for delivery to the UK.

Been using https://www.partsinmotion.co.uk

There prices and delivery are pretty good apart from random things that incur a delivery surcharge as I am in Inverness. If its skoda genuine parts then probably dealer or there is https://www.skoda-parts.com/ as well as https://www.lllparts.co.uk/ who also have original manufacturer parts diagrams and you can narrow it down with VIN.

Alasdair