Brought it in to Audi Slough.
Seems like issue with some control unit or something.. water inserted. They've replaced it for free under warranty.. then rang up to say they need another day.. so in total 3 days for service (engine oil change) then another 2 days to sort out this fan noise issue!! They needed a day to order the new part. Fixed it.. then realised they need another set of parts to complete it, thus another day delay to order.
Was annoyed with their lack of customer service.. had to ring them couple of times to remind them as to when they can get the car sorted by..