This information is copied from Parkstone YC Cruiser Fleet Webpages with their kind permission

The French Connection
Sailing pleasure craft to and from the UK (Border Force)
Sailing your pleasure craft to and from the UK (HM Customs)
Entry procedure for third-country nationals boaters (Port Chantereyne)
Ship’s Papers (RYA)
Pleasure Craft – UK / EU Entry & Exit Formalities (Lymington Harbour)