Within reason, I don't think we should get hung-up on charities' execs' pay. Comparisons with the PM's salary are, I suppose, meant to imply an excessive amount - how can a charity's CEO be paid more than the leader of the country? However, (according to Google) the PM's salary is £160k. The RNLI has an income just shy of £200m p/a, assets apporaching £1bn and more than 35,000 staff (incl. volunteers). Much smaller organisations than the RNLI in the private sector pay more than the PM's salary for their leadership teams.
I'm not saying the RNLI's execs do (or don't) represent good value for money (for me, VFM is the measure, not simply cost), but I do expect them to be capable and there's a far greater risk of employing under-skilled people if an organisation doesn't pay enough. Pay peanuts, employee monkeys? Of course, that's not to say a market salary guarantees competant employees!
Having looked at a few charities' CEO's salaries, some are startlingly high, but for most, given what is required of a successful CEO, I think these salaries are often good value. I am sure many people, if they had the capability to run some of these charities successfully, would choose to take a much higher salary with a commercial organisation.
I also don't understand the relevance of immigrants making boat crossings as a factor in judging the RNLI. The RNLI doesn't - and shouldn't - judge as to why peoples' lives are at risk, they just rescue them. That may be an immigrant in the channel (and a majority of them are later found to be genuine assylum seekers, not illegal) or, say, a thief that's jumped in the Thames to evade capture. We would be a pitiful country if our resuce service made subjective value judgements and didn't rescue people that didn't fit certain criteria. Ironically, the media would probably slaughter the RNLI if it did nothing and people died, and rightly so.
Some elements of the media love to bash some charities, e.g. RNLI and National Trust. No doubt some is justified, but much isn't. I have worked with a large charity and could level many criticisms at it, however most would stem from employing people with a lack of commercial awareness and/or experience. But the people I have worked with act in the best interests of the charity and its supporters; criticisms directed at them are often twisted to make a good media story and/or based on misrepresented information.