Tony: I think I mostly use the UK pronunciation...I think it 'flows' more evenly (sanwich...w/ a silent 'd'. Actually, we don’t really pronounce letters...we 'read' them because some of us have a 'habit' of pronouncing sounds).
I just usually call it by the ingredients. like Ham & Swiss on Rye, or Bacon, Lettuce and Tomato, or Grilled Cheese ... and leave the word "sandwich" to be understood in context without having to say it out loud.