I replaced my sagging headlining in the SEC today. The actual headlining board was good, the material had come unstuck. To do it properly you need to remove the complete headlining from the car, which isn't as bad as it sounds. The old material came off easily and I bought some new headlining material from a company online, it's actually jaguar headlining, but that's fine! I carefully stuck it back on with the right glue, refitted and am very pleased! Ran out of time to get the sunroof panel back in, but that's to follow. A DIY job well worth doing.