I saw a photo of a Lightning pilot (in the 70's) not apparently wearing G-trousers. I asked the gent in question (who had posted the photo of himself) and he said he was wearing them but underneath his flying suit.
That makes sense. As I recall it external g-suits (for wearing over flying coveralls) probably first made an appearance in the RAF in the very early 80s. Even when issued with an external set we had to also retain the internal set for use under the immersion suit.
Anyone remember differently or offer a better estimate on timescale?