Right took car in yesterday morning, got call about 11 saying cr is done and can we go and collect. Get in there and they cant find any knocking noises

Even though it is very intermitant.
The road noise issue was that he checked wheel bearing and said they were ok but rear 2 tryes were slightly distorted and recommended we replaced them. Ok fair enough i thought as they look quite old. Tread ok still but had the car 6 months now and done 16,000 miles.
The front 2 they said were slighty wearing on the inside so they said get the tracking, wheel alignment done. Ok i though.
VW qouted like £300 for the tryes and wait for it £ 99.95 for wheel alignment!!!!!!!!!!!!!!!!
Why would they charge £100 quid??? anyone know? please reply..
So took car to local garage and got quote on 2 new tyres, firestones, which were same as on the car and explained to them the situation, he came out checked tryes and said there was v slight distortion there but wasnt sure weather it was the tyres and didnt want to charge me for 2 new tyres in case it didnt solve it. Anyway he said let me swap fronts to backand vice versa, take it for a run and see if the noise is still there. Did that and noise was still there but coming from the front now!!!

So got 2 new tryes fitted and wheel alingment (£22.00 NOT FECKING £100 AS VW QOUTED) and car is now running smoothly.
Just want to get the knocking sorted now even though its very intermitent.