Had to think carefully about which Motorhome we wanted when we bought it, re space. We chose an Auto Trail Mohawk as we wanted two sofa/bench seats and lots of floor space. The dogs have had special safety harnesses made and travel on fleeces, placed on the sofas. They can climb down on to the floor and lie between them if they want to, but can't get as far as the cab area. At night they sleep on the sofas without being strapped in. (Great burglar alarms!). - We stayed on Motorway Service Areas in France and Italy on our way to and from Greece but never had a problem.
The Ridgebacks were walked each night before bed, so I'm sure anyone contemplating a break-in would have seen them and thought twice!
We didn't want a van with a Continental layout, as they mostly seem to have a fixed table and a 'picnic table' seating area, (not sure of the correct term!), which takes up so much floor space!
The Mohawk is 7.5m long and has a big 'garage' for carrying all our 'stuff', especially as we took 7 weeks of dog food away to Greece with us!