144hr Visa (using Hong Kong as external country) to return again back to mainland China

is London - Shanghai (3days, using 144hr visa)

Shanghai to Hong Kong (stay in hong kong a few days)

Hong Kong to Beijing (stay Beijing 3days on a 2nd 144hr visa)

Beijing back to London (returning home)

Please advise if the above itinerary is possible using Hong Kong as exit of mainland China to then return back several days later before returning home to the UK