I remember the 5 car Adelantes, that in theory were going to run as 10 car trains to increase capacity. In fact a single 5 car unit was used instead of an 8 car HST▸ .
I remember standing from Castle Cary in a 5 car Adelante to London (buses instead of trains from Taunton, numerous bus fulls of customers attempting to find seats on a new shorter train. I know of no reason why a full length train could not have been used)
Sorry, where do you get this from? The Adelantes were always intended to be used as five-car formations most of the time, with 10-car trains formed up for a number of peak workings. They operated in this manner pretty much the entire time
FGW▸ ran them. And when they worked on the main line for the first few years, they were being used to provide extra services, not 'instead of' HSTs
Given that you mention buses, presumably the occasion you refer to was a Sunday - perhaps an HST failed? Perhaps someone thought a 180 was better than leaving people stuck at Castle Cary? Who knows?
The other drawback of new shorter trains is that it is seldom viable to have a proper hot buffet, and certainly not a restaurant. The provision of 2 full buffets would be excesive, and having some trains with catering and others without would be too complicated. Better to just have a trolley !
Now remind me, exactly how many full restaurant services does FGW operate? Indeed from May the only proper mainline restaurant services left in the
UK▸ . Er, four, on a route that will continue to be served by HSTs. Travelling Chef type meals may pose more of a challenge but the eight-car sets would probably be able to accommodate decent catering space - and FGW is now a bit of an oddity in offering anything like this type of catering to standard class, even across a buffet counter, so with another operator a trolley might be all you would get anyway, whereas FGW provided a decent mini-buffet in 180s, far superior to the awful Voyager 'shop', and has provided something similar in the 2+7 HSTs.
Seating capacity-wise, a refreshed 'low' density eight-car HST is about 470 seats, with a 'high' density 2+8 just over 520. With loss of some first class seats and a few standard ones to the mini-buffet, a 2+7 may be 500-ish. A 180 is about 280 seats, so 560 for a 10-car pairing. As for 165s, I would challenge ChrisB to fit 275 incarnations of himself comfortably into a 165!
A fact sheet was released by Agility last year
http://www.agilitytrains.com/assets/pdf/AT-090205-Key_Facts-Released-1_5.pdf referring to previous versions of
IEP▸ - but still with 26m coaches - gave a capacity of 351 seats for a high-density five-car electric set, which is probably the basis for the bi-mode with underfloor engines (probably not allowing for a buffet, but even if you did fit one, still plenty more than a 180 (a 5-car 221 is 250 seats). The then 10-car 'self-propelled' set, ie an HST replacement with power cars at either end and with eight passenger coaches, seated 550 in Inter-City configuration, while an 'inter-urban' layout pushed that to 580.
There is no plan to build anything for IEP now other than 8-car all-electric sets and 5-car bi-modes.
