According to this, Labour needs a 0.77-point lead in order to catch up the Tories in terms of seats (with a uniform swing of 1.59). That's bad, but not too bad.
They need a 7.22-point lead to win an absolute majority. Tories only need a 3.29-point lead. Now THAT is bad.
2 things that could mitigate this problem:
1) A Lab almost-majority is probably more stable than a Con almost-majority. SNP, Plaid, LD, Green will certainly be bigger and probably more cooperative than DUP/UKIP.
2) A large swing to Labour is likely to produce more seats than uniform swing would suggest. It happened this time (Labour's vote was more efficient than often predicted), and their Liverpool/North London vote shares are pretty much at their ceiling; the swing would have to be from elsewhere.
So I would be wary of saying the SNP or Plaid would be more stable partners than the DUP. There is a real danger atm in the talk of a "Progressive Alliance" in which the SNP/LD totals are de facto thrown into a Labour pile. All of those parties are highly divisive at the moment, and if Labour is explicitly running on a coalition with the SNP next time that influences the dynamics of the election, both in Scotland and England, much as the very fact Corbyn is running for PM does.
Labour probably wins an election tomorrow or next week. But there is zero chance of that occurring. The coalition Labour won is far less coherent than that the Tories managed on Thursday, and it seems more likely to see a retreat in London Remain high income areas or low-income leave areas than advances in both simultanously.