Longevity of fresh mayonnaise- The two-day recommendation is from a cookbook of mine. I don't really know.
We never used vinegar, always lemon juice. Looking at the net, using a bit of wine is in several recipes- seems to be a good variant.

I think people worry overmuch about the eggs. All of the eggs sold in our area come from controlled egg farms. I haven't heard of anyone contacting salmonella, etc. from eggs here for a long, long time.

I think the main source of cold and other viruses is from infected customers in the stores, handling the merchandise, coughing, and waving dirty Kleenix around. It is not the produce but the customer.

Thanks for the tartare recipe from the Beeb (BBC). I haven't looked at their cookery site but I will.