Before Jetties became the norm, it was standard practise to use the ventral stairs for both embarking and disembarking passengers (especially if seat numbers pre-allocated it made boarding a smidgen quicker) Although it was also standard practise to ensure Passengers using the Ventral Stairs didn't duck under the wing by Posting either a Passenger Services Agent, or Cabin Staff Member at the Wingtip.
As I have just put built a Laker AIrways Tribute Album for Caz Caswell's Web Site I have a photo to hand :-)
Copyright Caz Caswell 1975 used with Permission.
As for rearward facing seats, all the 500 Series configurations I seem to remember included one row next to the overwing exits that was rearward Facing. 99Y 104Y, 114Y and the dreaded 119Y with Seat Back 'Catering' and the various sub-versions plus the 8F 80Y. OK its a long while ago and I may be wrong. Some Passengers on the Scheduled Service would chose the rearward seats even if seats in the Forward Facing row on the other side of the emergency exits were available.
As for the BUA/BCAL 1-11-200 series 79Y was standard although I remember a F Class Configuration was used I cannot remember details, or if either had a rearward facing row for the emergency exit.
Laker Airways were all 84Y for their 300/400 Series Aircraft and again I cannot remember if this required a rear facing row to allow for emergency exit clearance.