Well done, this is definitely a sea urchin (echinoid). A useful site written by the expert is :
The echinoid appears irregular from your image, but I cannot see the important diagnostic part at the top (it looks a little damaged?) . Examine your fossil carefully from different orienations and then look at Echinocorys Leske, to see what you think? These echinoids are common from the Upper Cretaceous.
Hope this helps a little,
Thank you very much for your help, I will use the link to do some further research and post more pics when I am back home later this week.
Your'e welcome Ken - I hope it is useful. If you are anywhere near London, you could bring it into the NHM and I would be happy to have a look at it and support you in your further research. We have specimens that you can compare yours with, infact, this is what the museum collections are made for!
All the best,