The moral of the story is, "the only purchase you regret is the one you don't make."
What you saw was probably a rifle built with trials rifle parts at Fazackerly in 1940/41. The left over parts from Enfield were sent there to be used up in starting their production. As has been discussed here before those rifles had A suffix serial numbers to designate the use of non-standard (ie: ex-trials rifle) parts.
A VERY RARE rifle indeed. Perhaps even rarer than genuine trials rifles.
Frankly, I'm amazed it was still there when you saw it at that price. :yikes:
I very much doubt it still is. In fact I'll bet a few people who've read your story are on their way there now!