Hi PAXboy,
A quick search on Google provided some answers.
More detailed history on post-War civil flights:
http://www.answers.com/topic/raf-bovingdon
History of Bovingdon airfield:
http://www.bovingdon.org/bovairfield.asp
Quote from the above site:
"There were also several civil Operators using Handley Page Hermes and Avro York aircraft."
Another site:
http://www.rafupwood.co.uk/recollections.html
Has one line related to Bovingdon - "Bovingdon airport was used by Silver City Airways for the occasional flight to Europe."
Regards,
David