Yes, the seat configuration is unchanged and seating 3 is fine.
No I measured and cut to my own requirements, I was unaware any plans existed.
All my materials were sourced via wickes, screw fix, b&q, ebay or internet. I am happy to provide links where I can.
Questions & answers about kitchen units, stoves, fridges, heaters, water tanks, seats, mattresses etc etc.
When you say either of the bench seats, not the rear most as the box sits on that bench seat