For those heading back to Brum, shall we all try to fit on one train for the comedy / companionship value then, or is their some worth in us picking different train times so not to upset the operator.
Chiltern run some of their Mainline* services using "proper" trains with an engine pulling real carriages. Whether this means a real guards van is questionable, but would be worth investigating. Their normal service uses DMUs, albeit posh ones that are sometimes quite long. As Robgul says, space should not be an issue.
*Which may or may not call at Banbury, I'll check...
Edit:
http://www.chilternrailways.co.uk/travelling-with-us/taking-your-bike"Where do Mainline trains stop?
Our fastest Mainline trains travel at peak times depart from Birmingham Snow Hill, calling at Birmingham Moor Street, Solihull and Warwick Parkway only, before travelling non-stop to London Marylebone.
Every hour, a Mainline train starts at Birmingham Snow Hill, calling at Moor St, Solihull, Warwick Parkway, Leamington Spa, Banbury and London Marylebone.
Also every hour, an additional Mainline train departs from Birmingham Moor Street, calling at Solihull, Dorridge, Warwick Parkway, Warwick, Leamington Spa, Banbury, Bicester North, High Wycombe and London Marylebone." I assume it works the same way in the opposite direction(?).
Don't forget there are additional, non-Mainline Chiltern services...