Information according to https://en.wikipedia.org/wiki/British_Rail_Class_414
1: top speed should be 140kph, not 121kph.
2: the capacity for first and second classes in the rear car appear to be inverted.
In reply to 1: source (https://web.archive.org/web/20071014060052/http://www.therailwaycentre.com/Recognition%20Tech%20Data%20EMU/EMU_414.html)
Yes, it seems the BR units were allowed to do 90, rather than 75. If you want to fix it and reply with a pull request, maybe James can look over the discussion and decide based on these what to do.
In reply to 2: source (https://www.webcitation.org/6fWP6Ee9w?url=http://www.southernelectric.org.uk/features/historical-features/brfleet_hap.html#)
1st class always had 18 seats in compartments. The amount of seats is 38 initially as compartments and then becomes saloons later on, seating 50 (a seat was added to the end compartment of 1st, making 19 seats). The 44 is halfway, I presume in order to reduce variance in the stock and allow simpler management of vehicles. The capacities are actually inverted, I agree so they will require fixing.
Pull request here: https://github.com/jamespetts/simutrans-extended/commits/master
I also made some adjustments to comfort and loading times consistent with BR mk.1 compartment carriages.
Thank you - now incorporated.