Thanks for all your input!
Doctors are often poor uninformed souls - I should know, I'm married to one. (I see her regularly....)
No, you just have to do what you think is best. And certainly don't let yourself get in the clutches of a high tech specialist. Good for his new BMW, but no good for your health (well, sometimes they do perform miracles, I admit...).
Anyway, I have chosen to go with this protector available from here
http://www.proaccessories.com.au/products/forcefield/torso_protection.htm
At only 1.5cm thick, it should be able to slip inside the wettie or under the rashie (comes with straps).
I'll see how it goes once I get back on the water.