Dont forget that to do a cross channel you will need ships papers (SSR), VHF license (for a fitted or hand held), ICC and VAT receipt!
There are lots of threads giving advice for cross channel.
As mentioned earlier, the slip in Dover can be a bugger. Lots of swell from the ferry traffic will bump you around while trying to launch, and is very narrow for the larger boats. My 5.4 goes down either side the wall depending which way the winds blowing. Launch and recovery could be done at mostl states except low +/- 2 where you will be on the softer sand at the bottom that only just holds a Discovery
. Slipway is steep and not advised for non 4x4.
When were you thinking of going?