Ofcom not thinking - as usual
FM can be received on simple low cost equipment with long battery life. (For years Poundland sold FM radios with earphones for £1.) DAB radios are much more complex, costly and power hungry. FM radio reception is built into many phones (provided that wired earphones are used - the phone uses the earphone wire as the aerial). In areas with low signal strength DAB fails completely but FM degrades more gracefully. Many cars on the road have FM radios not DAB.
The only reason for Ofcom to want to push for the end of FM broadcasting is that they hope to sell DAB broadcasting licenses.