I don't really agree that the NHS offers the best advice ...
You're not supposed to eat runny eggs because of the risk of salmonella. But the risk of salmonella is stupidly low and salmonella does not cross the placenta so it doesn't harm the baby.
You're not supposed to eat soft cheese because of listeria. Listeria does cross the placenta and would harm the baby but only 2 people have had it in the UK in the last ten years, so your chances of getting it are so low that, while I 100% understand women who avoid it regardless (after all, who loves soft cheese that much?!), it's not being irresponsible at all to eat it anyway.
Alcohol, of course, is another contentious issue. The safe limit is not known, but countless studies have shown that the odd glass of wine with your dinner will have no effect at all. Even if you binge drink throughout your pregnancy the risk of Foetal Alcohol Syndrome is (I think) 1 in 1000. 1 in 1000 is obviously quite high considering how many women are pregnant and it's obviously common sense that getting drunk, which damages your own body, is going to carry a high risk of damaging your baby's development. It is linked to low birth weights too. But there is no proof (and not for want of looking) that drinking a small glass of wine every day with your dinner will cause any problems at all. I have to say, though, I'm not drinking anything anyway 
Similarly as others have pointed out the advice changes because research is notoriously difficult in this area and its results are often very tentative and likely to be revised at a later date. So peanuts were out until recently because some small-scale studies suggested they might cause nut allergies. Until another research group realised that peanuts are staple ingredients in large parts of India, where there are also very low nut allergy rates ...
Basically the NHS goes with the most cautious interpretation of the data possible, and I completely agree that our babies are so important and precious that we're probably being very sensible to heed it. But those women who take it with a pinch of salt are not being irresponsible or silly, either - at the end of the day, not getting drunk, not taking drugs, not smoking, and everything else in moderation is just as safe a bet.
So I say relax, do what you feel comfortable with, and enjoy it!