If they've got facebook, my builder, checkatrade accounts etc. leave an honest review, pointless slating them, just say what you've said on here, the rest of there work was fine but tiling standards fell well short of british standards. Maybe some of floor tiles cut to make a skirting board around the floor could cover the gap, I haven't seen the tiles used but sometimes it can look ok, better than grout, is the grout used gonna blend in the tiles or add a contrast? Add some pics for us to see you'll get loads of ideas to stop it looking bad!