We always use this site when using the Tunnel / Dover Ferries both in and out of the UK.  We can't find a good safe site in northern France and this works for us really well.  We tend to arrive late and leave early so our only contact with the wardens is on the phone and we pick up our envelope when we arrive with all the information.  It always works well, the site is well looked after, the wardens are courteous and helpful on the phone.  It does what it says on the tin!  One day we will call, meet and thank the wardens at a civilised hour.