Hi there, I found this fossil on lepe beach in southampton. Not sure what it is. Any ideas?

Post's pictures

1441106021077.jpg, 1.84 mb, 3264 x 2448

I'm not 100% convinced it's a fossil, but my best guess is that it is a section through something like a coral or a sponge, hence the various rings (i.e. these are cut through tubes).