As reported in Wrecks of Liverpool Bay Volume II, I have found (and dived on) small pieces of wreckage from the Ellan Vannin. The wreckage above the seabed lies at the position given and to the SSW of it. Sonar plot (distances in metres):
I have also made a magnetometer survey which shows that the amount of magnetic material under the seabed is consistent with being the Ellan Vannin.
The figure shows the distribution of magnetic energy at the surface with distances in metres from the position in the book and magnetic north is up. The wreckage again appears to lie oriented SSW.