Hey DjC, I/we feel for you
.
With regard to unit versions (which I and MJMP posted before). V1.38 refers to the EPROM NOT the hardware build (although it is indicative to a degree as the early units were that version EPROM).
The v1 hardware build is discernible by it having the top inst/line level output switch and the line level rear jack input. They are still good units (if they've been looked after) and it's an easy change to put in the later (last) v2.01 EPROM.
While the later hardware revision units came with later EPROM revisions (eg EPROM v2.00), the hardware changed a bit ie no top switch and rear jack input inst level (there were other minor differences as well
IIRC from what MJMP and others have told us).
So don't necessarily discount/rule out the V1 hardware out of hand. eg the unit I sold MikeB, it's v1 with top switch. I bought it new in the day then did a gazillion gigs with it. Along the way I put in a v2.00 EPROM and a pair of SPAX7 tubes (around 21 years ago). Mike decided to give it a modernisation as they are getting quite old, so he got a bunch of bits from MJMP: So it got a new (stock) tube board (albeit with upgraded state of the art components), some new caps (noise mod, unfortunately electrolytic caps do die/degrade over time
), MDRT (this wasn't essential but really opens up the units dynamics), rear jack mod (worth doing as it also replaces the front jack which gets 99% of the ware and tare), battery mod (no brainer, the original batteries are so old now, that they lasted so long is just amazing). Mike also bough a complete set of jacks for the back panel (as MJMP still has them), he hasn't swapped them in yet. He also put a Mullard short plate re-issue in V1 and I gave him a SPAX7 for V2 that I had spare after my first MP-2 tube swap(s).
I get your frustration though, if only the seller(s) was/are honest about the unit and it should be priced accordingly. I wouldn't expect to buy a MP-1 with nothing to do to it (unless it's already been done, and then I'd prefer to do any upgrades it needs).