Now I've spent far longer than I thought I would have to researching what these suits are and it keeps coming back to them being known as G-Suits. I was looking for something more specific than that as 'G-suits' is a bit of general term covering a number of different types and styles. Rather than delay publishing any longer we'll adopt the general term for now and I promise to come back and revise the post if anyone offers me names, codes, dates etc. For now I'll share this with you from the doctorwhoconcordance.wikia.com
"The new Cybermen costumes for this story were created by Richard Gregory of Imagineering, in collaboration with costume designer Dinah Collin. Nine Cyberman costumes were made in total - eight full costumes plus the Cyberman seen fused to the door in Part Three. Previous Cyberman costumes had been designed around rubber diving suits, but Richard Gregory suggested basing the new design around G-suits. G-suits were designed for aircraft fighter pilots to help ease the rigours of flying at high speeds and encountering G-force. The suits had a network of connected pipes and tubes that could be supplied with pumped water to keep a pilot's body temperature steady and to press the skin inwards to retain the body's shape during periods of low gravity. More importantly, Gregory knew that his local army surplus store in Oxford sold G-suits. Another factor in the use of G-suits was that they looked slightly sophisticated and futuristic to begin with due to the in-built network of pipes and tubes and only needed spraying silver to complete the look."
I'm led to believe these suits are near impossible to get now and certainly not from the high-street. It's possible that the materials have perished over time or simply that hundreds of Doctor Who fans all wanted to make their own costumes.