I've just got GHDs. So now I become one of those people that boasts about the superiority of GHDs to kid themselves into thinking they were worth £100. I've got a good 2 years left until they dutifully break, so I'll use them well and inflict 7 years of damage onto my hair.
The GHD 'Creation Spray' that I bought with the straighteners will not, however, escape criticism. It claimed to be able to hold your style better so I read the reviews which somehow made me believe it was something other than just hairspray.
It is in fact proactively worse than hairspray, and the only perceivable result is more of a delightful burning smell than before. I have thus concluded that any advice or information you will ever receive from anyone is born out of ulterior selfish motives and noone's opinion can be trusted.