Thanks to a random video that popped up on my instagram feed I’ve found that the put put sound on tickover when warm is a broken ?vacuum? hose.

Any pointers as to part number for this?

https://www.skoda-parts.com/spare-part/05e133366dt-ventilation-pipe-with-akf-valve-skoda-46956.html

Found it on Skoda parts. But also found another post where @imart143 said that he used 3m self amalgamating tape to repair it so I will give that a go before spending £170!