So just to provide an update in case anyone was suffering the same problems........
So after getting the AUX belt changed the noise persisted, this was narrowed down to the cambelt area. Having looked at the Service History and seeing this had been changed 18 months ago I was fairly confident that it must be something else,. However I was faced with having no option but to book it in again so they could have a look at the belt and pulleys.
What was revealed was a cambelt which appeared to be fitted on the car from new! Very worn and with 3 big splits in it. The mechanic was shocked to see the condition of this and confirmed this is not how an 18 month belt should look! Once replaced car is now noise free.
I'm not on here to point fingers or accuse anyone but something is clearly not right here. Maybe I was foolish to believe everything I see in a service book. I will certainly be more cautious in the future.
Having seen the cambelt with my own eyes I was very disappointed, but relieved that I spotted this when I did.
Steve.