Had a bit of a google with your reply and very impressed with what is out there (even if it is just a bit OTT for my current family day sails). Memory map.co.uk gives a free trial which I will play with some time.
Finally as a bit of a cheat for locating shallows I have uploaded some piks of East Head, Itchenor reach and Spinnaker tower I took out of my brothers microlight……..have a look at
learn-to-fly.co.uk if anyone fancies a trial flight!!! (it was “awesome”)