LO2 stopped napping (through sheer force of will rather than what she needed!) around 2 y 5 mos, she needed to nap really but didn't want to. On days she did nap BT was no fun, messing about, not sleeping til 8.30 etc. So we stopped trying, pushed through, and went with EBT at 6pm/6.15. Well over a year later she is still going to bed at 6.15/6.30. So I would drop the nap, and go for an earlier BT, maybe 6.45/7? I was surprised to find myself with such an early BT for her but it worked a treat.
The interesting thing for us is that LO2 is now very good at saying she wants to go to bed early, if she's not feeling well there have been days when she's been in bed at 5pm (and more or less slept through).