splodge O/T: I would be very surprised if you couldn't invest your £400 per month better than in a poorly performing pension scheme. A £4000 p/a return at the end of your working life is not good, as you point out. Have you taken financial advice? Your profile says you are in your early 30s, so if you can save that much now, there's a good chance that there are better options available to you.
I am in the public sector. I am on a final salary scheme. It is decent, but it is also "deferred pay". My sector recognises that it underpays for the skills it needs (e.g. a doctorate), so the pension is an integral part of the package.
When I was finishing my PhD, I was headhunted by a number of different firms and companies. I turned down their generous offers in favour of my current job because I was following my interests and at the time had ludicrously idealistic notions about my role in life (had not yet found Mumsnet & Xenia. If I had, I think now, in retrospect, I would've taken her advice... ). My public sector paycheck is many times less than those which were offered to me from the private sector. Had I followed the alternative route open to me, I could have, by now, saved as much as will be available to me in my pension pot when I retire in c.35 years time (my scheme, like any other, is really only "worth it" if I stay in it for a long time). Wiser friends of mine from university, in their early 30s, have already "retired" from the city jobs they took when they left college.
It is not a zero sum game, btw. When I say, "yes, I deserve my pension" it is not to say that I therefore think you do not deserve a good pension; I do not think I am worth more than you, or anyone. Of course not. It is a scandal not that the public sector offers a good pension scheme (which would, I admit, be more affordable if the sector were streamlined and made more efficient), but that the private sector has been allowed to railroad over the needs and rights of its employees.
And incidentally, my pension scheme is - like any other scheme - involved with the stock market, in property portfolios, etc. It is not the case that the each person's pension is paid entirely from the public purse in a direct manner. Yes, my employwer pays an amount equivalent to 16% of my salary (and I contribute 6.35%) into the scheme, but the scheme is then managed like any other. Furthermore, and perhaps this comes as a surprise, the scheme is already under threat from our employers who plan sizeably to reduce the benefits of it, etc. Public sector pensions are not as "gold-plated" as they appear; only those of the top ranks of the sector. And those in the top ranks do well in any sector.