The Tories winning 25 fewer seats would leave them as the largest party in a hung parliament, a simelar position to the one they found themselves in post 2010 in OTL.
That probably rules out a minority government with DUP support alone, so Major probably needs supply and confidence from the Libs at the very least.
Would Major and Ashdown be amenable to the idea of a full coalition? I suspect that Major would be, given his OTL views on the Coalition-and I think Ashdown would also be open to entertaining the idea. Whether Major and Ashdown could get their respective parties in line is another matter-I'm not sure if the Lib Dems could be persuaded-the one big difference between 1992 TTL and 2010 OTL is that in 1992 the Tories had been the governing party for the past 13 years. Furthermore, Thatcher's supporters would be reluctant at best to back a coalition with a left-of-centre party after 13 years of complete dominance.
Still, I don't see Ashdown backing Kinnock if Labour aren't the largest party, so I think some sort of supply-and confidence deal is the most likely outcome, with the implicit understanding there would be another election 18 months down the line at the latest. This, of course, would be bad news for the Conservatives-and for Major in particular.
Black Wednesday will happen on schedule and Major will be no-confidenced, so there will be another election in October/November, which Labour will win with a comfortable majority, though not a 1997-esc one.
Now to Labour-does Kinnock remain leader post July 1992 in these circumstances? On one hand, it is likely there will be another election in the very near future, so would changing leaders at this point help? On the other hand though Kinnock would still be seen as having snatched defeat from the jaws of victory as Labour would still have been the favourites to be the largest party. Their's also Kinnock's personal views to consider-having lost 2 elections, did he have the stomach for a third election campaign as leader? I can see it going either way really, but I've got no doubts that either Kinnock or Smith will be PM by the end of 1992.
I'm not sure who is Tory opposition leader after they lose the late 92 election. Hesser probably won't be leader given his bagage, perhaps Hurd could be in with a shot though?