Before the pullover sweaters became the standard, cardigan sweaters were issued. Those were the WWI period items but I don't know when the switch occurred. But WWI style service dressed was still on issue in a few units until the new No. 2 service dress was introduced in the early 1960s. Some units went to France in 1939 still wearing service dress, battle dress not having been issued to everyone by then.
Some of the little details of changes are very hard to pin down because they are mostly minor and notice of such changes sometimes consist of little more than one paragraph in a bulletin. As an example, the Lovat Dress uniform, which was a service dress in a greenish khaki mixture introduced sometime in the 1960s and is still worn today, originally had quite full trousers. Uniforms invariably follow civilian styles in some ways but always at a distance. Anyway, there was a one line notice in some bulletin that future procurement of trousers would be narrower in the leg. Even so, not everything is even that well documented, if you call that well documented.
Some of the little details of changes are very hard to pin down because they are mostly minor and notice of such changes sometimes consist of little more than one paragraph in a bulletin. As an example, the Lovat Dress uniform, which was a service dress in a greenish khaki mixture introduced sometime in the 1960s and is still worn today, originally had quite full trousers. Uniforms invariably follow civilian styles in some ways but always at a distance. Anyway, there was a one line notice in some bulletin that future procurement of trousers would be narrower in the leg. Even so, not everything is even that well documented, if you call that well documented.