Some 15 years ago G read about this in a magazine and really wanted to go - but it's a long way from Australia and Margate is 90mins from London. Still, the time came and we got to Margate. C didn't have high expectations of the grotto or Margate so he wasn't disappointed - unlike G. Basically it is a casual walk to the middle of Margate and then another 10-15mins to explore the grotto. The grotto's shells are dark - stained from candle smoke and probably age - so it isn't visually exciting. Because of the lack of definite historical information about the grotto it is hard to assess the accuracy of the curatorial work. As far as I could see it is not wheel-chair accessible and probably not suitable for people with mobility problems.
Is it worth it? Well, if you happen to be in the area it is an enjoyable 20 mins and at the end of the day, how many shell grottos does anyone ever see? So, if you are going to visit any, Margate's is probably as good as others.