I have been in contact with Lexus US, Lexus Sweden, Denso Netherland and Denso U.K. The message I have gotten is that a Navtec map DVD that fits my Lexus RX 330 does not exist.
All have provided good answers. I am positively surpriced about customer service from all of the companies. However I still think this is a market limiting decision more than anything else. I have looked at Navtech DVD's for Europe (not working in my unit though) and compared file structure with myUS DVD. It is the same type of files, same structure, everything. If they wanted to provide a Denso compatible European map I really think they could do so with a minor effort.
The reason Aisin is not pin compatible is due to TP-RDS enabling traffic jams to affect the navigation routes. That is only available in Europe. So even if I would spend £4,000 I have no solution. The only remaining alternative is to buy a £200 unit and have it loose in the car.
PeO.