Just thought I'd pop back in this thread and share my experience of sunburn!
I got sunburn really bad in Majorca a few years back. It was so bad that I ended up getting a heat rash as well, and had to see a Doctor. Not exactly the best way to spend your holiday!
Since then, I take better care to keep covered in the sun. It's better to stay protected than to risk getting badly burnt and ruining your summer.