I can't find any obvious maps of that kind.
However, you can use ordinary contour maps. Many maps show land of different heights in different colours. If you look at the lower edge of each colour, this will show you the coastline at a sea-level of that height.
In several previous interglacial times, southern Britain was flooded to about 30 m (100ft) above current sea level, and to lower levels even more often (see for example
http://www.geographypages.co.uk/sealevel.htm).
You do need quite a large scale map to show contours close to sea level -- the lowest contour on my Philips atlas map of Britain is 100 m (about 300 ft), which is way above what is likely even if global warming gets very much worse.
There is one map I found which shows part of the English south coast:
http://www.scopac.org.uk/maps/sealevel.pdf (my house is under one of the inset maps...). The main map shows the results of just a few metres (5 or so?) of flooding.