Thank you clemmy, I was in Portimao in 2006 and it doesn't sound a great deal different! There was a couple hauled out alongside me who ran an old British registered car, and had done so for nearly a year with no problems. However in the marina later another Brit told me he had been warned 6 months max and required to leave with his vehicle. At that time I don't know what the situation was with boats at all though.
I was planning on spending less than 6 months in Portugal but had thought I might fly home and ride my bike back down there for winter transport. Thanks for the website, appreciated.