Northern have 3, so we can discount those.
Unless the 322s get reclassified as a sub-class of 321s?
Although, Metro have a guarantee that the Metro stock (144s, 155s, 10x158s, 321/9s and 333s) will remain in West Yorkshire until at least the end of the current franchise (which DfT have extended to Feb 2016.)
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A little bit of an outlandish possibility... But if some/all 323s were replaced by 319s at Northern West, then 323s could release 321s from London Midland...
Would need to be a lot of changes to allow that, because
1. Apparently there are some platforms on the Glossop line which have platforms around 75m in length - long enough for a 323 but not a 319.
2. Apparently the 319s can't match the 323 timing on some routes. A proposed solution to that is for the 319s to become 3 car (to reduce weight) and be re-engineered but then a 319 would be smaller than a 323.
3. Apparently there are no plans to train Piccadilly crews on 319s until the next franchise and the 323 routes are Piccadilly crew routes, so someone would have to fund extra crew training.
The 321/4s don't actually have significantly more standard class seats than 323s (some 323s even have more than some 321/4s) but the 323s lack First Class, so I think LM taking on 317s or 319s would be a much simpler solution.