12 miles from Walton might put him well out of range of his VHF? Plenty shallows out from Frinton/Holland. When CG think use of mobile inappropriate, they often say so, with usual homily, but not this time ...
Our family have carried a VHF on our yacht for 10yrs and have never used it once, now i have mobile and VHF if I was to get in trouble i would try the mobile first if no success i would then use the VHF