To remove a 554 port number you just have to remove :554 from the URL. You should get the following URL:

rtsp://rmv8.bbc.net.uk/news/olmedia/n5ctrl/tvseq/od/bbc1/bb/rm/video/panorama_bb.rm?start="00:04:20.0"

Please try to record it in the URL mode and let me know if the problem persists.