I think that the tricky thing is that during this regression you start to tweaking the routine, decreasing the nap, or moving BT, and maybe the lo doesn't really need this, it is only a phase that will pass (and of course, due to the lower amount of sleep, some OT is involved), but if you make too many changes and cut too much the sleep, in the long term you have an OT lo in your hands, more difficult to handle.
I have to admit with our last regression I feel I actually made things worse for Z by tweaking but not just holding back and making one small tweak, then holding for a week.
Personally I would maybe try pushing the nap out by 15/30minutes, leave everything else as is and then hold for a week. For us chatting at BT after 12 months for 45mins was totally developmental and OT from me trying to push him out too much suspecting UT.
HUGS Reni - We are all jsut trying to give you some food for thought - Its hard as LOs are all so different and after 12months they become tricky wee things.