As an aside, I'm convinced my current calculations are wrong. Every pension planner says I need £xyz p/a income for a comfortable lifestyle. I consider my current lifestyle to be comfortable - I'm soon off on my 3rd foreign holiday in a villa this year, so can't be grumbling.
So how come my current (heavily played about with via salary sacrifice schemes, so see how little I can live on*) income be very significantly lower than what the pension providers' calculators say, and I still feel comfortable?
I'm convinced I've missed something very fundamental 
*Done it this way, as we all know you spend what is left in your account 
The illustrations given by pension companies assume all sorts of stuff that may or may not be relevant to you. The rules are set by the FCA, and mean that every company should give their illustration in a way that can be compared to others, so it's not the pension co's fault. This usually results in very low estimates based on low returns, such as annuities. An annuity provider must pay out even if you live to be 150, but the FCA assumptions are for a negative rate of return after inflation on you pot, and this means you need a big pot to sustain a small payout.
Annuities do have a place for those with no appetite for risk - you are basically paying the provider for a guaranteed income, so the risk is all theirs. However, if you are comfortable with some risk yourself then you can (probably!) achieve a better outcome by using one of the more recently introduced pension freedoms like drawdown. But, if you stuff it up then you could end up penniless in your old age - which is another reason to get an IFA involved particularly if the pots are large.