You'll be fine mate. Sludge is not as much of an issue in England as it is the US, our fuels are different. The 2.0 engine is not as bad engine, they are fairly low stress so it's really doubtful there's any sludge there. If the dealer has been using Castrol 10w-40 then it's been on fixed interval (12 month/10000 mile) servicing.
Fixed interval oil recommendations are
Engine oil VW 500 00 SAE 5W-30 All temperatures
Engine oil VW 502 00 SAE 5W-30 All temperatures
Engine oil VW 500 00 SAE 5W-40 All temperatures
Engine oil VW 502 00 SAE 5W-40 All temperatures
Engine oil VW 500 00 SAE 10W-30 All temperatures
Engine oil VW 500 00 SAE 10W-40 All temperatures
Engine oil VW 502 00 SAE 10W-40 All temperatures
Engine oil VW 501 01 SAE 5W-50 All temperatures
Engine oil VW 501 01 SAE 10W-50 All temperatures
Engine oil VW 501 01 SAE 10W-60 All temperatures
Engine oil VW 501 01 SAE 10W-60 All temperatures