I still don't get the thing about MPs not travelling in First Class. Long ago I understand one of the aspects of being an MP was you were given a First Class season between London and your constituency because you would be frequently travelling to and fro. The pricing was agreed centrally between the railway and Westminster, it wasn't the full fare season price because they obviously didn't make the return journey every day, just as and when.
The government stipulates in their franchises that significant amounts of First Class is provided on long distance trains. Just who do they think this provision is for? If it is for "business travellers" that I would have thought that senior government members, of whatever party, are in the business of running the whole country, and thus certainly qualify.