Just ready to set about tiling round the new kitchen cupboards and
trying to decide the neatest way to finish the tiles where they meet
at an external 3 way corner. This is the corner where the window
ledge, the wall behind the sink and the wall to the back door come
together, IYSWIM.

I have seen this done by amateur and so-called professional tilers
using plastic tile trim. The best seem to cut a mitre on the two
horizontal edges but leave the vertical edge to but up against the
other two. This leaves a sharp point on the mitre which protrudes and
doesn't look very good.
The worst aren't worth describing.

Any ideas of the best way to do it?

TIA
Pete