We are considering taking the ferry from Calais to Dover and renting a car in Dover. Any advice from previous experiences?
What is the best way to get from Paris to Calais?
You can get to Calais ferry from Paris by train, but it's not cost or time effective.
Have you thought about getting the Eurostar tran from Paris to London, and then travelling on from there, either renting a car, getting a train, or some combination?
You haven't said what you are planning to see in UK.
If you give us a bit more info, we can make more suggestions.
it sounds like you are hoping to cross the Channel by ferry as foot passengers.
Unfortunately that is not as easy as it once was.
There are three large ferry companies between Dover and Calais/Dunkirk providing passenger services, but in great measure that is for passengers in/on their vehicles - cars, motorcycles, campers, etc., as well as freight.
The three companies are Irish, DFDS, and P&O.
Only P&O provide foot passenger transportation, and only on a few of their daily crossings, and none from Dunkirk (served by DFDS and no foot passengers). They don't make it easy. In addition, the Calais and Dover train stations are quite a long way from the ships. I could go into much more detail, but let it be said that if you don't have a vehicle using Eurostar between Paris, Lille, or Brussels to London is much easier. That's the train which go through the Channel Tunnel.
Can you elaborate on your plans a bit further? Where will you go by car from Dover?