The Buxton, Mid-Cheshire, Liverpool-Manchester via Warrington and both Southport lines have Northern services which need >160 seats without any further passenger growth. (I know Pacers can't go to Buxton but it's a line where a 2 car DMU is not sufficient at peak times.
There are going to be 150s and 156s freed up by electrification that could be used on the lines that you suggest - it's not "Pacers or nothing"
Around 45 minutes ago I saw a 2 car Pacer depart Knutsford with around 170 on board. How would that work if it only had 80 seats? Maybe leave 40 on the platform?
You've said on another thread that this was due to the crowd at an annual fair (the one that George Osbourne tweeted the "clown" picture of, presumably?) - a known event on a Bank Holiday when there would have been spare stock (which Northern didn't use).
That's surely not the kind of basis to make long term plans around - equally I could suggest that we need eight coach trains on the Penistone line due to the number of Barnsley supporters who travelled through to watch their team play at Huddersfield on Saturday, but that wouldn't justify that level of service every day of the year for similar reasons.
Will ScotRail release any 158/170 units south?
Once Dunblane/ Alloa are done (later this decade) ScotRail should have freed up around fifty DMUs (the main Glasgow - Edinburgh "shuttle" needs sixteen 170s at peak hours - the combined Glasgow/Edinburgh - Stirling services require a similar number, plus there's the "southside" and "suburban" stuff around Glasgow like Cumbernauld, East Kilbride that should take the number to around fifty).
There'll be a desire to keep some of the spare capacity in Scotland - understandable - either to increase capacity/ introduce new services/ get rid of the loco-haulage on the Fife Circle - but even if no new DMUs are ordered that should free up dozens of Sprinters to England and Wales.
Will Turbo cascade be adequate for West of England?
The North Downs route should need ten 165/166s (I think it's eight units plus one peak extra plus one for maintenance) and one for the Greenford shuttle, but apart from that almost fifty 165/166s could be freed up by the end of the decade - quite a lot when you consider there are only eight Pacers left with FGW.
Whether they all fit on current 143/150 operated lines is another story I suppose.
What do you think the Calder Valley services and those services from Manchester that will run via the Todmorden Chord from 2014 onwards to Accrington/Blackburn will have as their rolling stock by the end of the decade ?
Probably something similar to the mix of Sprinters today (155/ 158) plus some freed up 185s from Transpennine electrification?
Manchester - Blackburn is almost exclusively Sprinter operated at the moment (used to be 100%).