The question is, who did the
saying. Presumably it was the PRC. In that case, 'Having said that' is fine; it means 'After
it [the PRC] had said that...'
If the person doing the saying is the writer of the sentence, 'That said' is better (in the opinion of some sources - who dislike having participles lying around not referring to anything). It means 'It having been said' - impersonal, so it doesn't need to fit in with any other part of the sentence
Having said that, I must add that many native speakers aren't aware of this; that some who are either don't care about it or believe strongly that it doesn't matter; and that others who would prefer to 'get it right' (in the terms used by their schoolteachers back in the '60s and '70s) don't.
b