Oh good my post appeared below after a short delay – I mustn’t be so impatient!
Anywy, whilst waiting I found a thread that explains the potential problems with the SW version of BL3500: https://archivedforum2.beoworld.org/forums/t/20499.aspx
Any here’s an FAQ about BL3500 SW updates: https://www.beoworld.org/faq_view.asp?id=80