Hi stroppy, Visual GPS is full of unnecessary additional apps and other stuff..I wouldn't recommend it on such vintage device
Here, try this one, but before you do any changes, make sure you do a full backup of your mio flashdisk.

Code:
Please Login or Register to see the links
PS: It's not my work I just find it in my archive and it looks like good choice as it is simple unlock menu for Mio C520.