Hi again, Thanks for the responses, particularly from dadiOH, Big Jake, Jim, and C.C. I pretty well have in mind what I have to do now to accomplish the task.
To those who say that marine ply is overkill, I'd point out that the reason I'm using it is for the same point a couple of you raised about water leakage and swelling. The marine ply will negate that. My one concern is to ensure I get ply that isn't too wet, as I don't want it drying out and warping/shrinking after the job is done.
As for the anonymous poster (aren't they always?) with a fixation on hygiene, is there anything intelligent or constructive to your posts that had any relevancy to the question that was posed, or do you simply have a problem reading English? Most counter top materials can pose health risks unless meticulously maintained and cleaned. Porous stone counters that don't have the seal maintained can harbor bacteria, as can wood counter tops. Prepping food, such as cutting up meats or vegetables, on counters such as corian or laminate can damage the surface and create scratches that can also harbor bacteria. Many stone counter tops can also be stained relatively easily unless care is taken to prevent the problem. And as for the direct point about tile and grout, as someone else has already noted if both are well sealed and maintained the problems inherent with the medium should be no more or less of a problem that certain types of stone used for counter tops.
Your pedantic point regarding chicken is also presumptive BS, as we're vegetarian, and while you may be happy dumping baking items all over your counter top to make cakes we prefer using wax paper, regardless of the surface we're using. And if you're trying to suggest that you place your salad items directly on the counter top before cutting them up I'd suggest it's you who has the problem with hygiene. Like most people, I wash all of my fruit and vegetables under a tap before placing them on a cutting board (or directly in my mouth) to clean off any chemical residues or dirt that might still be in place as a result of the growing process.
In short, if you can't contribute something meaningful and pertinent why bother going to so much trouble to demonstrate your blow hard tendencies and irrelevant prattle? Do you really like seeing your views on display that much? You've contributed nothing of substance, just a leery if somewhat skewered fixation with hygiene that would have made Howard Hughes proud.
Rest assured that your points about gagging over food prepared on tiled counter tops has been noted, as has your point about the fact you'd never eat such food - is that before or after you've gagged, by the way? I can't tell you with what regret we'd have to accept the fact you'd never call round to our meager little home for a meal with our family as a result. After what I've read here I can see that we'd undoubtedly be missing out on one of the greatest experiences of our lives.
Cheers..........Tim