"quite a lot of the ultra people and ironman lot take salt tablets"
they tend not to be just sodium though (but I guess you know that Hipps!) but are the full electrolyte tabs/drinks........
IM events tend to have an interesting mix of things at the run aid stations from gels and energy drinks to crisps, nuts, bananas, flat Coke etc through to what I think is a life saver - chicken soup (well, more a chicken bouillon)...........when you crave some salt and a change from sweet and sticky gels and energy drinks, the chicken soup gives a real lift.............should be compulsory in marathons!