Hi David!
Many thanks for the reply. Our browsers are already set to English UK, I have also just added american too (going on your thought train), but it hasn't had any effect.
I know that DVWP's don't render UK dates (they forgot to add the uk time code in SP Designer!), and because this occured when we upgraded to 2007 I thought this may be a known bug they simply forgot to account for.
However, no-one else seems to be having it so I am assuming everyone else can see the weekday in UK Calendars?