You might be interested to know that you can sign up (free) with the Channel Coastal Observatory to have email alerts when the waves exceed certain conditions.

There are a number of buoys on the network with one at  Gwynt y Mor in Liverpool Bay. Go to the link below and click on the “Alerts system – receive custom alerts from the observatory” option. You can then set a wave height and/or wave period to trigger an email when the sea state reaches that level.