Dennis
Thanks for your reply and links. I set up WPMU for subdomains because they were 'Geshmack du jour' at the time. Today I have configured the sub domain de.mysite.co.uk, which i think will be easy to add to WPMU domain mapping as a new separate site. I was unsure how to do it so that mysite.co.uk/DE is seen as a completely separate site from mysite.co,.uk in WPMU.
Funny that the site TLD starts with 'journey' and so, using sub-domains, reads 'de.journey', which is rather French ;) Maybe this is no small point and I have to look at directories again...
Rgds
Bhakti