The nice thing about a Thorley Exhaust header is the fact that it will not crack as easily as the cast-iron header. BTW, this cracking is a problem on both the 1.3 and 1.6 exhaust header.
The bad thing about the Thorley header is, as someone has already mentioned, that you need to modify the downpipe connection on the exhaust system.
Also, there were at least two different types of 1.6 16-valve exhaust headers. If you get one from t the junkyard, you may end up doing some fabbing if you get the wrong one. Been there, done that.