Leisure Travel makes twin bed models. The LT Wonder (Ford diesel chassis) has two opposing sofa's that are also twin beds or can be combined to make a king. I guess you would call these a B+ as they are wider.
Some of their floor plans offer a slide. Like JaxDad mentioned, there is a floor plan where the rear is a living space that also turns into a corner bed.
One thing I like about LT, is that they have full bathrooms with a separate shower. I like the rear twin bed model on the Sprinter chassis as the seating/eating area is in the front along with the two captain chairs. The rear beds could be used like a sofa if needed or relaxing to watch TV.
Good luck,
MM.