They seem to have a glazed edge , so trim is down to personal choice really , which he should have offered you in fairness. Again as regards the layout stacked or brick is up to the customer. Agree the joints are far to small , with a wider joint I also think the edge of the tiles would have tied in better to the overall effect ( if they are indeed glazed ).
All that said, to add the trim , I'd pop off the whole cill and reveals to achieve your desired finish , can't see it being to much off a problem myself .Couple of hours , few extra tiles and a little bit of care and attention should sort it out.
Diggy :0) - Merry Xmas all by the way!!!!!