h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

The following site shows maps of the UK, showing the likely impact of certain sea levels. You can select a theoretical sea level rise via a drop down menu.

www.flood.firetree.net

I was surprised to see the extent of the changes in the UK with moderate increases in sea level.

At a macro level Devon, Cornwall and West Somerset appear very recognisable except at the very extreme (although it would clearly be a disaster for all coastal and major river towns).

I was interested to see how quickly the Somerset levels became a sea (predictable answer - very quickly), showing how insular the peninsular would be.

However I was surprised at how much the eastern part of England simply disappeared, and how much extra space the Severn estuary consumed. Ireland was also majorly impacted.

At very high levels (60m) Cornwal breaks up into a series of islands, and Plymouth, Torbay and Exeter are significantly reconfigured.

Not directly Celtic in any way, but sobering nonetheless.