Ok, here's my breakdown on Joe's career stats, in terms of home away fights:

From 43 fights we have:
17 fights taking place in Wales
in 27 of those he would be considered a home fighter, against someone from a foreign country, or in Wales,
8 would be considered as Calzaghe being the away fighter,
and 8 (mainly in his career build-up) where he appeared on the undercard on fights in England against an English fighter.

And during his reign as champion (including the fight where he won the title.)
10 fights took place in Wales.
2 fights were on neutral territory.
1 fight was outside of Britain.
4 fights took place in England, in or near the hometown of opposition fighters.
Therefore, in my breakdown I would say in 15 of 21 fights, he was the home fighter. 2 fights were on neutral territory, and in 4 fights he was the away fighter.

Considering that he is the champion, and naturally champions will make the majority of their defences in their homeland, as that is where the core support is, so I reckon Calzaghe hasn't done too badly.