Thanks sirs,
I'm really learning a lot with this post and my initial plan was to buy from the Dell Website Dell Axim x51 with all GPS kit included (West Europe map, antena, car kit, and so), but maybe it worths ($) to buy only the PDA from Dell and the rest separeted. For that I would like to know what else I would need but the GPS in order to compare if it really worths.
Here in Switzerland, PDA + GPS from Dell.com costs CHF 950,- (£395)
Only PDA Costs CHF 454,- (£189), so I would have £206 to buy in addition.
Checking www.totalpda.co.uk main page:
MAP: TomTom Navigator 6 Software - European maps: £89 (includes SD 1GB and software, correct?)
Carkit: Carcomm Powered PDA Mount for DELL X50/X51 range: £44
Receiver I had a doubt between:
Bluetooth Receiver Navman SPiN 100 - GPS Navigation system: £19 and offers a so called Atlas Maps (additional? Replace European Maps?)
or
Holux GR-230 Bluetooth GPS Receiver no Box: £39 (only receiver)

In worst case I would save £34 (CHF81,-)

In best case £54 (CHF130,-)
Can somebody tell me about the receivers?
Is that all or do I have to buy something else?
Is there some other option (cheaper) for the separated kit?
Is it a good solution? Compatibility problem?