On another matter, is there any way of getting Train Line powered websites to give the ^154 fare? They all seem to quote journeys on Virgin as they overtake LM▸ , which means they show only ^200+ tickets.
Yes, put in via Hemel Hempstead.

That'll bring up 2 of the 4 LM services from
MKC▸ to EUS per hour (the xx22 and xx47). Nothing stopping you using the xx05 departures which are fast to Watford Junction.
EDIT: And I think you won't beat the Super Off Peak Return (LM+
FGW▸ ) with GroupSave fare. I've had a look at various options to try and get you and your friends on a Pendolino as well as the usual split points. Nothing doing without increasing the cost. One of those journeys where splitting is only likely to yield savings if it was a Day Return.