The overcrowding guidelines are summarised in the DfT» FOI▸ reply in the recent thread about FGW▸ 'top ten' services.
Ah - thanks. Got it -
http://www.firstgreatwestern.info/coffeeshop/index.php?topic=8288.0Basically, for services that have no stops within 20 mins of the major [London] terminus, the capacity is just the number of seats, and no one should stand at all. For stopping services the capacity is generally seats plus a number per m^2 usable floor area.
So the official answer to SDS Pad's question, at least in relation to services from Paddington with a first stop or Reading, is
Everyone should get a seat if they want one, though they may have to move down the train. The official answer on Reading -> Basingstoke, where there is standing allowed for (less than 20 minutes, not departing from London) is less clear when it comes to questioning who should be seated and who should not.
Sorry - SDS Pad - this doesn't give you folks at Paddington a practical answer when you have people fighting over seats!As an aside, if the rule is different for services from London that don't stop within 20 minutes and all other services, does that mean that CrossCountry trains are at liberty to apply the local level (standee) loadings on even their longer distance services.