That being said, what Exists? The us edits or uk edits?
Hopefully all the alternate edits of The Max Headroom Show exist somewhere in the world!
I've just spent a few hours scouring American TV listings to get the original broadcast dates for the US shows. I was surprised to find out that the UK TV Movie that premiered 4th April 1985 in the UK, was shown on the Cinemax cable channel in the US, just 10 days later, on Sunday, 14th April 1985. Over the next two years it was shown a dozen times, before being remade with an American cast, and set in New York, instead of London.
The Max Headroom Show featuring music videos with the occasional special guest made it's debut on Wed, 16 Oct 1985, 7.30-8.00pm, with each show being repeated on Saturday afternoon, and again on Tuesday night. It ran for 10 weeks with the final show getting its first airing on Wed, 18 Dec 1985. These shows would have been similar to Series 1 and 2 of the UK Max Headroom Show.
The following year the format was changed to a chat show with another 10-part series debuting Fri, 1 Aug 1986, 10-30pm-11pm EST (Guest: Michael Caine). These appear to be the same episodes that were broadcast the following year in the UK, so although 5 of them are now listed as "missing" in the UK they should still exist over in the US. Unusually, instead of weekly, this show was every two weeks (with four repeat screenings in between on different days and times), so the last episode (Guest: Jackie Collins) had its first airing on Fri, 5 Dec 1986.
On Thu, 18 Dec 1986, there was a one-hour edition, entitled "Max Headroom's Christmas Special", that aired between 5.00pm-6.00pm EST. This presumably is the same programme that was called "Max Headroom's Giant Christmas Turkey" when it was broadcast by Channel 4 in the UK a week later! So the Americans got the 10-part chat show first, even though it had been filmed in London, followed by the Xmas Special. In the UK we got the Xmas Special first, and then the 10-part chat show.
Now, on to 1987. This was the year Max Headroom went mainstream, with the first 6 episodes of the ABC show, airing every Tuesday from 31 March 1987 until 5 May 1987. Cinemax then decided to build on this popularity with another series of the chat show, this time filming it in New York, matching the location of the ABC series. So as not to confuse viewers who might be expecting the sci-fi programme, they called it "The Original Max Talking Headroom Show". Once again, it aired fortnightly, and after perusing various newspapers I've actually managed to get the original air-dates and guests for each show:
THE ORIGINAL MAX TALKING HEADROOM SHOW
Thu, 23 July 1987, 10.00-10.30pm. Jerry Hall, Penn & Teller
Thu, 6 Aug 1987, 10.00-10.30pm. Mary Tyler Moore, Robin Leach
Thu, 20 Aug 1987, 10-00-10.30pm. Ron Reagan Jr, Paul Shaffer
Thu, 3 Sep 1987, 10.00-10.30pm. Bobby McFerrin, Dr Ruth Westheimer
Thu, 17 Sep 1987, 10.00-10.30pm. Don King, Emo Philips, Madeline Kahn
Thu, 1 Oct 1987, 10.00-10.30pm. Grace Jones, Gilbert Gottfried, William Shatner
It's a shame Channel 4 didn't pick this up and broadcast it over here. I do hope that the master tapes still exist and that they'll get another airing someday...
Note that there are a couple of guests listed above that aren't mentioned anywhere else on the web!
The ABC Series, Max Headroom, returned for a second season on Fri, 18 Sep 1987. Unfortunately, ratings were poor and it was pulled from the schedules on 16 October before the last 3 episodes were screened. Two of them were aired the following year but the final episode was only ever shown in Australia, and was unavailable in the US until the DVD release in 2010.
So there we have it, 3 UK series, 5 US series. I suppose I should update Wikipedia again to include this information...