I guess potentially you argue the toss that it's rarer than the two US copies.... so, on that basis some lunatic will probably pay £50,000............not!
Seriously, would anyone have a clue what it would fetch... even John M wouldn't know. This is all based on the seller (owner rather than John M) either having a reserve of what they think is a realistic price or simply chucking it into the market place to see what it goes for. Personally I don't think acetates count in the value of records as they are a sub-genre, unique maybe, but not a record as such. But thats only my opinion of course and it counts for nowt in many cases
Best
Steve