The Admiralty provide free seven-day forecasts for ports around the UK. The seven-day forecast for Port Askaig can be found here: Port Askaig
The position of larger vessels can be identified by tracking Automatic Identification System (AIS) transmissions. These are publicly broadcast on VHF radio and the data is collated by a number of useful websites such as www.shipais.com
Wind and wave forecasts are available from a number of sources such as the SeaStates website from APBMer. APBMer have also produced a number of reports to quantify the wave and tidal resources around the UK.