Having Gloster stop building Gladiators earlier is relatively easy. Most of the Gladiators built IOTL were built after they delivered heir first Henely.
603 Gladiators were ordered for the RAF and RN of which 22 were cancelled, 15 went to Portugal and 6 to Norway. 225 (including the 22 that were cancelled) were ordered in the 1935/36 financial year, 78 in 1937-38 and 300 in 1938-39. All 98 Sea Gladiators were in the 1937-38 and 1938-39 orders.
So still order the 225 original aircraft as Gladiators, but order 578 Hurricanes instead of the next 378 Gladiators and the 200 Henleys.