Train help

Those trains don't have reserved seating- they are local trains, not long distance.

If you are travelling outside of commuter hours (commuters into London) as you will be then there will be plenty of room.

The 'fly in the ointment' at the moment is that there is bridge work happening on the railway to Oxford, on the way to Moreton.

This means that you take a train from Paddington to Didcot Parkway, then rail replacement bus to Oxford, then train to Moreton in Marsh.

The suggestion/recommendation is that you use the alternative rail route to Oxford from London Marylebone, and change there onto a train to Moreton- those trains from Oxford are running on their normal timetable.

On the national booking system it will show you a through train from Paddington- that is not factual, but they are only changing the national timetable weekly for that route even though it is a fact that the line does not re-open until at least 10 June.

In time terms it is probably about the same. It is just your choice if you want a bus in the middle, or a 2 train route. Either way you ca still book a through train ticket.

when are you travelling, and how many in your group? It sounds like Groupsave may work for you

You would normally expect to be able to reserve seats on London to Moreton-In-Marsh but I suspect with the bridge closure that seat reservations may have been suspended. You might be able to reserve at least part of the route using an account with GWR, or at a station.