"I won't be applying for the job though, the salary is less than i get working in construction"
I know of tempory typists that earn more than the salary on offer. Likewise temporary lab assistants / technicians. Many bus drivers start on more money than GCHQ offer...
Also GCHQ offices are in places where nobody on that salary could aford to buy a one bedroom flat let alone a house these days. So either have to live in comparitivly "squalid digs" or still live with their parents etc and travel long distances, often at inconveniant times.
Also due to Maggie Thatcher (80's Conservative PM) you are not alowed to be part of a union to protect your employment rights etc.
The big draw for many in the past was that they knew that if the kept their "nose clean" and did a competent job they would have job security and a reasonable social and retirment package hence they were known as "lifers". Which David Cameron (current Conservative PM) and his cohort of "free market thinkers" has decided is "to generous" and "the country cannot aford it" (whilst giving multi-billion tax "sweethart deals" to his and others "big business free market " chums so they have 1000GBP+/hour deals lined up)...
And although GCHQ do offer training it's very much a "sup with the devil" arangment. So it's still a "dead end job" because the skills are not only "non transferable" you are not alowed to talk about them (ie put them on your CV) or use them if you do leave.
Also back in Maggie's day the "security services" used to stick their nose into your private life big style, as some people found out their friends, relatives and previous employers and educators did not take kindly to being visited by a couple of heavies asking personal and private questions.
Thus the GCHQ employee ended up issolated with little or no life outside of the GCHQ Community (which made the security services job much much easier, thus having "outside friends" was looked at as "not keeping your nose clean")...
Hence GCHQ like a big University provided a substitute and used to have (as David Camerons cohart regard them as "needless expense" to be expunged or made to pay the comercial rates) many societies and clubs to cater for the "social needs" of the GCHQ community.
And as far as I can tell the historic result was that outside of admin staff there are two types working there both of which appear on the outer tails of the normal distribution curve of personality types.
That is those strongly showing the traits of Aspergers and the other group / extream showing the sociopathic tendencies of "political animals", give you a guess which set gets the senior grades and better pay...
As a country the UK will in future times pay dearly for the mindless stupidity of the current and previous governments, because of their over riding narcissistic sociopathic behaviour. As publicaly exhibited by their self absorbed illegal greed (expenses scandle, cash for questions, honours for cash, etc, etc) and very very short term outlook, thus they are much like serious drug addicts, who can only think of their next fix and not able to see how it gets them deeper and deeper indebted to their "dealers".
So like you I certainly won't be working as a "Sararīman"  prone to "Karōshi"  for them any time before hell is on the other side of absolute zero.
 Sararīman : Japanese term for a salaried male worker, literlay "Salary Man" in recent times it has become purjative and equivalent to a "White collar wage slave", or one likely to die from Karōshi .
 Karōshi : Japanese term for "occupational sudden death syndrom" in apparently healthy white collar workers supposadly in their prime. Literaly it means "death by overwork", on autopsy the usual cause of death is attributed to one oof the "silent killer" diseases caused by significant stress. Japan is one of the few countries that actually record these deaths as a seperate statistic. In the UK something like half of non accident/violence deaths in otherwise healthy individuals under the age of 50 are from the "silent killers" with no apparent causal factors such as smoking or obesity. In some places it's sarcasticaly refered to as "YDS" or "DYS" for "Yuppie Death Syndrome" or "Death by Yuppie Suicide".