Vantage 2007 Sat Nav

[MadMacMcMad]

My Satnav cannot find any satelites. I have been told that it is the CD unit that is at fault which is an arm and a leg to replace through Aston.
Considering the SATNAV system is woeful and inadequate, I do not want to spend money on it. Sois there an alternative that anyone has upgraded to?
Or has anyone already upgraded and would like to part with their old system.
Thanks for your help.