Habitat:
In British seas, and on the shore when the numbers can reach epidemic proportions, the Common Starfish, Asterias rubens, is the most prevalent conventional starfish of the N.E. Atlantic Ocean. It is an Arctic-Boreal species with a maximum temperature tolerance of about 22° C.
Usually found on the mussel beds offshore. 
Behaviour:
Its principal prey is mussels (consuming them in their shells), but it will eat fish eggs, carrion, and other molluscs.

Starfish consuming a Cockle

Starfish feeding on Mussels

Asterias feeding on a Grey Topshell

Enemies: Common Sunstar, Crossaster papposus.

26 March 2008
After a recent bout of northerlies in North Wales I took the dog for a walk down on Red Wharf Bay on Anglesey and found all sorts of things washed up. Common Starfish, Asterias rubens,  were very abundant, as a rough guess at 5-10 per square metre, amongst the rest of the wreck.

23 March 2008

To qualify as nationally newsworthy a CommonStarfish stranding must be in tens of thousands. 

Sussex Marine Life Reports

4 -5 March 2008
Hundreds of thousands (perhaps many more) of Common Starfish, Asteria rubens, were washed on the shore of east Kent.
Picture Link

1 January 2007

Common Starfish on the chalk bedrock at Seaford
Photograph by Wednesday Livingstone

22 May 2006
Thousands of dead Common Starfish, Asterias rubens, were seen on the beach at Lydd-on-Sea, Kent. All the starfish were strewn along the high tide line, and for every step I took I passed 20 to 30 dead starfish. I walked about half a mile along the beach and the line of dead starfish seemed never ending in both directions. Some of the starfish were laying on the sand and in the sand pools but these too were dead. Also, about 30 Sea Mice, (an annelid worm), Aphrodite aculeata, were found washed up dead.
NB: This discovery followed two days of gales. 

28 January 2006
Thousands of dead specimens of the Common Starfish, Asterias rubens, were washed up on the beach about a mile and a half to the north of Tywyn on the Cardigan Bay coast of north Wales.  There seem to be various interpretations of these mass strandings, including winter storms and changes in water temperature.

17 March 2002
Thousands of Common Starfish, Asterias rubens, were washed up on the beach at Holkham, Norfolk, on the east coast of England after sustained north-easterly gales. 

31 December 2001
Thousands of Common Starfish, Asterias rubens, are discovered washed up dead on the shore at Formby, Merseyside, Lancashire.