For best fit rather than rock bottom price, it's easy, I have been using skoda-parts.com for many years, parts by Skoda/VW number, checked against your car's VIN, either original part or a decent quality alternative (often a choice of both), and you can still ask them further by sending a message if you are not sure. Some things are worth getting from Autodoc though, as they can be a lot less expensive for premium quality, for example zinc coated brake discs. But you really have to triple check part numbers with Autodoc, both Skoda and specific part manufacturer's, and make sure you get sent what you ordered and not a cheap alternative. It can be a fuss with Autodoc, but can be worth £100+ on a brake disc order alone when compared to say ECP. As for UK suppliers, I occasionally use GSF or ECP as they are both local to me, but for any larger order than £50, like e.g. 2 quality rear suspension springs, I find GSF and ECP are often double the price of skoda-parts. I do not order many used parts, but I have used ebay on odd occassion for these. HTH