On slip roads that may be true, but for roundabouts no. Funnily enough I tried asking National Highways the other day about speed limits on slip roads (60 or 70) and they basically said "it's national speed limit" (i.e. no answer. I would presume the same for this case, so we can only go on common sense here, in that it's a single circular carriageway, not part of the dual carriageway.