The Stukas were radio-controlled scale models. I don't believe there was an airworthy example in 1968 when the film was made. I'm not sure there is one today. The Bf 109s were actually the Spanish-built Hispano HA-1112 Buchon. These are basically a Bf 109G with a Merlin engine. The He 111s were the Spanish built CASA 2.111. There is still no genuine He 111 flying anywhere in the world. The last remaining airworthy CASA 2.111 unfortunately crashed last year in Cheyenne, Wyoming, killing both crew members.
http://www.warbirdalley.com/he111.htmI believe this was one of those used in the film. Although some of these aircraft were still in service with the Spanish Air Force at the time & flown by their regular crews some were privately owned. Many examples were tracked down & purchased specially for the film by the late Group Captain Hamish Mahaddie.
http://dspace.dial.pipex.com/town/place/gdg18/battleofbritain.shtmlThese aircraft & the film itself were responsible for the renewed interest in restoring WWII aircraft & many are the ones we now see on the display circuits in various parts of the world. If it wasn't for that film many would have disappeared for ever.
I'm sorry you were disappointed with the film. I saw it soon after it was first released & have watched it many times since. Although I thought the "aerial ballet" sequences were a little overdone it was well made & I always thought of it as a classic. It gives a good idea of what the BoB was all about & how it affected the ordinary people involved.
PS. There was no example of a Spitfire Mk I or II available in 1968. The BBMF MkIIa P7350 is the oldest airworthy Spitfire in the world and the only survivor of the Battle of Britain still flying.
She is believed to be the 14th aircraft of 11,989 built at the Castle Bromwich "shadow" factory, Birmingham. Entering service in the August of 1940, she flew in the Battle of Britain serving with 266 and 603 Squadrons. During this period, on or about 25 October 1940, she was involved in combat with Bf 109s and forced to crash land. The repaired bullet holes can still be seen. She was quickly repaired and flew again on 15 November, only 3 weeks after the crash landing.