I think you are going to have to do your own research. Where are you starting from in the UK, e.g. Dover or John O'Groats? Makes quite a difference to the distance. What sort of car do you drive, e.g a modern hybrid doing over 50 mpg or a Mercedes Maybach doing around 20 mpg (if you're lucky)? Makes a big difference to the fuel cost. Which countries do you intend to drive through and what sort of roads do you intend to use, e.g. motorways in Germany are generally free while in France they cost? Which sea route do you plan to use, e.g. Venice to Patras or Bari to Igoumenitsa? The former involves the least driving but costs more for the ferry while the latter is a cheaper ferry but involves more driving. Does the ferry you intend to use from Italy to Greece also serve Piraeus to Crete? If so you get a discount on the second route, if not both are full price. So many questions and I am sure there are lots more.
I've done UK to Greece and back twice, once by motorbike and once by car and I've also done Greece to Bordeaux and back once by car. I haven't the foggiest idea what it cost or if what it cost when I did it would be relevant today. When I am doing a journey like that I don't spend my time writing down what everything cost. Some possibly useful web sites:https://www.anek.gr/en/https://www.minoan.gr/en/cretehttps://www.viamichelin.co.uk/https://www.rac.co.uk/route-planner/http://www.theaa.com/route-planner/index.jsp
PS If you decide to use ordinary roads in France please note that the maximum speed limit has been reduced to 80 kph even though the signs still say 90 kph. Obviously lower limits apply where signed.
PPS There is an area, usually on the top deck, next to the dog kennels, where dogs can relieve themselves and you are expected to clean up after them.