The rocks there are Devonian in age, and ammonites do occur in the Devonian.
But I have been unable to find one which fits with your specimen. Of course, beach gravel often comes from somewhere non-local - which does not help.
The last image on this page shows a similar sort of ammonite
Note the recessed keel and the way the 'ribs' sweep into it.
Anybody else care to comment?
Thank you so much for your help in identifying this. I am sure you are right... following your messages I googled more information and found this image which is so similar http://www.google.co.uk/imgres?imgurl=http://andysfossils.files.wordpress.com/2012/07/amaltheus-stokesi2_s.jpg&imgrefurl=http://andysfossils.com/2012/07/07/amaltheidae-one-of-my-favourite-ammonite-families/&h=686&w=1028&sz=139&tbnid=OBufTL0JfzlkZM:&tbnh=93&tbnw=139&zoom=1&usg=__uGueFcq187EjmukfNePtEdFwS1o=&docid=xlDPx6Lu2hdwbM&sa=X&ei=Rd8RUp2gGaS40QWnxYCgBQ&ved=0CDwQ9QEwAQ&dur=1407#imgdii=OBufTL0JfzlkZM%3A%3B9aLtDCz5qFKdBM%3BOBufTL0JfzlkZM%3A
I really appreciate your time and effort.
Nancy and Beatrice