The locking cylinder has been getting stiff and now it has seized completely

For the past few weeks the locking cylinder in my car had been getting stiff until the other day when It seized completely. The key will only turn a bit to let the steering lock off but wont go any further. I have tried most things bar taking it out or having it replace like manually changing the transmission from park to neutral and drive then back to park. I have tried lubricant but still noting. What would he the best option to sort this apart from going to a Volkswagen garage, but I will do if necessary.