We did it last year, and it was incredibly expensive, £1200 for the hire, plus rental costs for the campsite pitches, food, petrol and tolls.
Then if you are rolling on to a new place each day, you are constantly booking in, finding a good pitch, parking and setting up, unpacking in the afternoon. Then with the checkout times you are up in the morning, wash breakfast, washing up, packing up, driving on.
Then there is the stress of a big vehicle, and being careful with it for the insurance cover etc.
We'd have been better off and more comfortable staying in budget motels and driving in our car. At least we would have had an opportunity for rest and no housework!
We would love to visit DP's brother in Spain this year, and are thinking of hiring a Motorhome and driving down. We'd like to take our dog with us, so would like to find a dog friendly hire company with nice vans