Masson carded a second consecutive 67 at Buckinghamshire Golf Club to finish 12 under par, with Thai duo Titiya Plucksataporn and Nontaya Srisawang her nearest challengers after rounds of 67 and 69 respectively.
Peters held a two-shot lead after a superb 63 in the second round, but needed 14 shots more on Saturday to fall six off the pace, with Hull matching her playing partner’s 77 to finish four under.
After dropping three shots in the first four holes, Peters got back into contention with birdies on the ninth and 12th, but then pulled her approach to the 15th out of bounds.
The resulting double-bogey was followed by another dropped shot on the next and although the 21-year-old drove the green on the short 17th to set up a birdie, she also double-bogeyed the par-three 18th.
World number one amateur Leona Maguire is four shots off the lead after a third round of 69 featuring four birdies and just one bogey.