I haven't seen an explicit mention of the Iran-Iraq War in any post-1980 WW1 veteran memoirs or interviews. A common theme is a rejection of war in general (such as by Harry Patch in The Last Fighting Tommy) but I can't recall mentions of or attitudes towards any specific post-WW1 conflicts in any of the memoirs or personal accounts I've read (apart, unsurprisingly, about WW2).

By the time of the Iran-Iraq war even the youngest WW1 combat veterans were in their 80s, so the cohort was already fading fast. It also wasn't a conflict that was heavily reported in the Western media, so it didn't necessarily feature highly in the national consciousness.

So while we can imagine that any WW1 veteran who knew about the details of this conflict would be appalled and saddened, I think you would struggle to find any concrete evidence of their attitude towards it as a coherent group, even amongst those who were both aware of it and aware of the specific nature of the fighting.