Captain,
when you say Basseleg Hillfort do you mean Tredegar Fort?
If so, you can access it via Gaer Road. There is actually more to see there than Caerau Hillfort. It has obvious ditches/ramparts to see although it has become the local unofficial dumping ground! At Caerau it is mainly the later medieval ramparts and later ruined church to see.

I don't kniw about the one under a golf course?

regards,
Carl