Skoda Roomster front windows work intermittently

Hi there ive got a 1.6 roomster scout,the front windows work when they fancy??.ive had a diagnostics test done and only one intermittent fault found,interior monitoring sensors part no 5J0 959 433 A,ive spoken to skoda dealer and found out price ???.but they refuse to tell me where on the car this part is located can any body help please and if you know where the best place(price)thanks very much steve.