Where & how do I start teaching myself about pension funds?

IMO the biggest mistake an inexperienced investor can make is to start switching funds based on things like past performance (oh this one grew x% more than that one over the last so many years) or reading a few articles in the press, or responding to online posts.

Before you do any of that, the most important thing to do is to define what your long term objectives are. That way, it will help you decide what type of funds you need to invest in. You need to think about how much you will need your investments to grow to support your retirement. That will help you identify how aggressive you need to be with your investments. So do some proper long term planning before you start switching funds. Think about the impact of the state pension, any other savings and pensions you may have, and the level of income you will need to support your lifestyle in retirement.

At the same time, you can find out more about how funds work. You need to know the difference between active and passive funds, the charging structure they use, the "mix" of investments (higher "risk" funds generally have more equities as opposed to other assets like bonds), and also the difference between single sector funds and multi-fund funds (funds of funds). You can do some searches on here as a lot of these topics are discussed in detail. There are some good books as well, like Lars Krojier's Investing Demystified and John Edwards' DIY Simple Investing.

You also need to define your attitude to risk and couple this with the timeframe over which you need to invest. Higher risk strategies will likely give greater returns in the long run (10 years plus) but you could see big swings in the short term, including some big drops. You need to understand how you will feel if that happens, the worst thing you can do is to switch strategies as soon as the market drops.

Final word from me: I would be in a much better position if I had left all my contributions for the last 15 years in my company's default Blackrock Consensus fund choice. I made too many changes before I properly understood all of the above.

I’d recommend Smarter Investing by Tim Hale.