What about the 317s and 321s that FCC have, with the 319s being cascaded what's stopping the 317s and 321 from also being cascaded?
I still think FCC ought to have stayed with the 377s and order two batches, first batch for the TL and the second batch for the GN to displace the 319s elsewhere.
It's already been announced that the 365/313/321 are staying on the GN. The NXEMU are doing new services. (As for the Kings Lynn's services, anyone's guesses is as good as mine as IEP was supposed to be replacing these services!)
One thing no-ones mentioned at all on here is the fact that the new Thameslink (NXEMU) trains will actually displace some of Southern and Southeastern's trains as the new trains wont actually replace services but renew the fleet. For example one TLP is complete services like the Orpington to London will run off new stock releasing Networkers to be sent elsewhere.
As for the link between GN and TL, currently Network Rail has started work this month on lighting the tunnels prior to fitting out with all the signalling, track and OHLE.
Basic plan from memory is as follows
First 12 car NXEMU arrives and a years testing on line takes place. Unit will be based at Three bridges new depot.
The first 23 NXEMU (all 12 cars) replace the 23x 377/5 which return to Southern.
A mix of 12 and 8 car then come into service. So fact plans include trains from places like Horsham - Victoria (12 car) and Orpington - Victoria (8 car).
FCC recieve 8 car trains to replace the 319's on the Luton/St Albans - Sutton loop services. This services are the last to recieve new stock.
Note under current plans FCC will only be running 12 car new trains (replacing all Bedford - Brighton services) along side 4/8 services to Sutton and Kent destinations with Southeastern running 8 car NXEMU before FCC does!
Grant all this can and will likely change before we get to 2019 but it gives an idea of how these (upto) 1200 carriages will arrive.
http://www.dft.gov.uk/press/speechesstatements/statements/hammond20101125
As part of the Thameslink programme, we will procure a new fleet of trains up to 1,200 new carriages. This is in addition to around 600 new carriages which will be provided for the Crossrail project.
The new Thameslink and Crossrail rolling stock will enable the redeployment of hundreds of serviceable electric carriages currently used on Thameslink services. These carriages belong to rolling-stock leasing companies, but we expect they will be available at competitive leasing prices for re-use elsewhere, thus justifying further electrification of our network.
One last thing, How will Crossrail EMU's help release Thameslink trains? Or is this a reinforcing the point one to many times?