Is this like car insurance, where the first offer they give you is way short of the mark?
Not got any experience of PPI, other than telling all the "Claim Back Your Mis-sold PPI With Only A 30% Fee" nuisance callers to do one. I wouldn't have even bothered with my claim if the bank hadn't written to me themselves. Turns out they added it to a loan I once had, despite me telling them I didn't want/need it.
As they saw fit to squeeze as much out of me as they could I may as well return the favour, albeit this time within the boundaries of the law. I just don't want to waste any more of my time if the first offer is as good as it gets.