I heard they went into the 1960's, though unlikely they would have been the WW2 design.

I am no former AFV Crewman but there is certainly photographic evidence of them in use on Conqueror which would take us up to the mid 60s certainly. I don't recall seeing Chieftain crews ever wearing them but I do recall seeing a motorcycle escort rider belonging to a Tank Transporter Squadron here in Wiltshire in the (roughly) mid 80s sporting one. A good piece of kit will always be popular with troops if they can get hold of it and transcend normal kit issue longevity.

From a modelling perspective I would suggest Pixie suits for Centurions and Conquerors and the armoured cars and scout cars of the same period.

As far as I am aware there were no design changes throughout the suit's life. The camouflage version was also in service more than most think.

I am sure former British Army crewmen who populate this site will come up with more definitive answers than I.

Still being worn by at least one nco instructor at the School of Armour at Waiouru (New Zealand) in 1966. M41/Centurion and Ferret scout Car.
He was an ex Centurion crewman in Korea.

Canadian tankers wore them into the late 1960s on the Centurions.

Apropos the camouflaged version you might enjoy this small clip; probably best with the sound turned down but a typical film of its time:

https://www.youtube.com/watch?v=J7HnKmT2WgM

Of course, it doesn't really answer the question as it's taken in 1959, but may be of interest.

While I think about it Ultracast do a fantastic range of figures in 1:35.