Just to clarify for other people plagued with the BV8-40 DVB fan noise:
Software update to build 166d does not solve the problem.
DVB software update 0.1.7.1 DOES solve the problem. (recent start of DVB transmission enabled me to install)
The mysterious reason B&O say to contact your dealer if you "have a BV8-40 and live in the UK" is due to different types of module and software requirements. With the end user involved in updating etc it would be useful to be directed to the correct software simply by inputting the TV serial number on the site!
Thanks all for the advice - a quiet TV at long last.
David