My girlfriend and I stayed at Antonio and Rosa's apartment for a week and could not recommend it enough to anyone wishing to visit Seville!
Antonio came to meet us and showed us around the flat, which is just as beautiful as it looks in the pictures. The roof terrace is absolutely amazing and the views onto the cathedral were perfect. It's only 2 or 3 minutes from the cathedral and is very central.
There were a number of little things that show that Antonio and Rosa are great hosts. They had kindly stocked the fridge with a few small things, they had put together a great list of places to eat at and visit, and they got in contact with us every couple of days to make sure we were enjoying our trip.
In summary we would absolutely go back and would recommend to any young couple looking for a nice central place in Seville.