Hi,
going to paste a section of my reply from another siesta question.
I love siesta, the coaches are comfortable with films to watch good rest breaks and choice of music through the free headphones.
You may change coach at leicester forest, we did and then we went on to the eurotunnel for a 4pm crossing, when we got to northern spain the next morning there was another change for people going to costa brava, we stayed on the coach to the cye, Its nice to know your luggage is with you on your journey.
Food on the coach is ok, cheap and choice of hot or cold, sandwiches, hot dogs, burgers, tea, coffee or soft drinks also beer once outside the uk.
I have been twice with siesta and never had any problems.
Never stopped at sanguli only at the cye apartments (highly recommend)
Going back in october by plane and will probably go with siesta again next august (you can book now for next year already)
Have a good trip,
Simon