The twin leaf doors were fitted to some of the Berkhof bodied Tigers that London Country received. I think the bus grant had essentially gone by that stage. However, Green Line vehicles had since the late 1970s featured coach shell vehicles. These were AEC Reliances followed by small batches of Volvo B58s and Leyland Leopards with grant type features such as dual leaf doors, all on Duple Dominant or Plaxton Supreme bodies.
The 1980s saw them receive Tigers in large numbers with the awful ECW B51 body, some Duple Dominants that were really bus grant style with their destination equipment etc, Plaxton Paramount etc. That's because they were working stage carriage work (albeit limited stop) and didn't want the delays of plug doors. It was all part of the bus grant where, to get government funding for new vehicles, coaches would arrive with certain features to be used on bus services for a proportion of the year.
The Berkhof bodies were a real departure and in the first batch, some had coach type plug doors, whilst others had dual leaf doors as illustrated. Looking on Flickr, think the ones with dual leaf were for the 747 Jetlink and 777 Flightline services. I recall that quite a number of those Berkhofs were subsequently rebodied by East Lancs as buses for Midland Red North; must've ended up with London Country SW and passed through Drawlane Group!