Most people quite naturally associate the Battle of Britain with Spitfire and Hurricane pilots, but no less than nine (I believe) Blenheim squadrons took part, as well as Beaufighters, Defiants and sundry other types. All of their crews were entitled to the rare 'Battle of Britain' clasp. - TTN
Lest we forget:
The Fleet Air Arm and the Battle of Britain - History Learning Site 
Jack
PS Congratulations, Grandpa!