Hi,
I have been having a look around - most of the central hotels with secure parking are pretty pricey and they charge you extra for parking. I am sorry I cannot offer you anything myself.
There is a nice bike hotel about 25kms south, but then you would have problems getting into the centre (its Tronicek Hotel - it comes up on Google)
There are lots of private Pensions around the suburbs in the North in Villa style houses (I have heard they are very good) and the transport links to the centre are good. The place Dazzer stayed is in a good location.
There are lots of private secure carparks in the centre but I cannot vouch for them though.
Let me know if you want me to check anything out - I am off on holiday next Friday
Cheers