If the car has a full dealer-stamped service history then I would expect the dealer that sold you the car to make a 'goodwill payment' application to Volkswagen UK - it is unfair for them to expect you to cover this repair cost on a car that's just four years old.

The statute of limitations means you have rights for six years after buying the car (five years if you bought the car in Scotland), which means you may have grounds to demand a free repair. However, in order to do this, you'll need to seek professional legal advice and prove (beyond doubt) the infotainment was faulty at the time of purchase.

If you don't want to pursue this via the dealer or the small claims court then an auto electrical or independent VW specialist may be able to repair the infotainment system without replacing the whole thing.