I was faced with this dilemma, two feature strips, either side of wc and basin. tiles are 11mm, mosaics are 8mm.Oh and they want 2 silver square trims either side of the mosaics, these are 9.5mm. Normally I would try and put the trim under the tiles as it is too fiddely to bed out both trims and mosaics.
The solution: Make them up the night before
Ready to be fitted
The finished article