I would personally only use genuine VW stuff - or failing that, speak directly to Castrol Technical department on the phone. But I would never use any kind of general gear oil, nor a gear oil from Halfrauds, or any of the lesser known or cheaper oil companies.
Because even with genuine VW gear oils, they have over 30ish different types listed - so just like engine oils, it is not a case of 'one size fits all' for gear oils.
If you aint sure which genuine VW gear oil to use, you can PM me your VIN, and I will look up, and supply you the correct part numbers.
HTH