I had (and still have) one of the Fisher/Ritchey Montares mentioned above by Graham and I'm pretty sure I rode it at the Wendover Bash mentioned in the first post - my memory is not what it was!! I do recall the series was the "Fat Tire Five". I bought that bike from Evans in The Cut. It was preceded by a Stumpjumper Sport, which I sold on, and followed at the end of '84 by a Roberts custom frame, which I still have and ride. I bought the Stumpy and then the Ritchey in late '83. FW Evans were one of the earliest to have Mountain Bikes, if not the earliest; I remember seeing a pair of Stumpjumpers there (Magura Motorcycle Brake Levers?). However, they had a couple of bikes in at a time, rather than "available". They said something about Richard Ballantyne being involved in importing them, I think.
My brother had an early Evans, in 1984 - it was an excellent frame, in Reynolds 501. My recollection is that the Saracens and later Evans frames were not the same, nothing like as snappy to ride. Certainly these were amongst the first bikes but not the first. Madison were selling one too (Ridgeback) pretty early on. It was not in the same league, being somewhat heavy... It was, though, the first MTB that I ever test rode, from the Beta Bikes shop in North London, and as far as I can recall the first MTB that was generally available.
Takes me back a bit. Tony