What kind of pensions do you have? Are these all private plans or are there any old company/defined benefit schemes amoungst them?
Look at your asset mix in any managed funds inside your private plans and check the management fees, but I wouldn't be to fussed about having different providers as if the charge is a flat 1% say across each provider it's the same as having all your eggs in one basket with one company and less 'risky' in terms of provider 'stayability'.
Moving pensions around between providers could involve a fee..readjusting your asset mix in your funds may or may not involve a fee if they have a free annual switch, which I recall many did.
Performance in a pension fund is to a degree dictated by your attitude to investment risk. The closer you get to retirement the less risk you may wish to take, finally locking in the gains say a few years prior to your retirement date. Most providers have suitable cautious fund options available for that purpose.
I would assess my pensions in terms of asset mix first, are they spread across a good range of assets, including cash, property, bonds, equities etc. If you are looking for higher gains you may need to accept a higher risk and hold more in equities for example, and vice versa if you are more cautious and happy to accept lower returns. That is a very basic view and it will be different for each investor.
Many plans have a bog standard 'managed' fund option with 'medium' approach to investment risk as well as more specialised funds in higher risk areas. If the bulk of your funds are held in the standard managed fund option you should expect only standard returns. You likely have the option to switch exisiting funds and/or future contributions across several other more aggresively managed funds (higher risk) in an attempt to boost gains.
Clearly there are no guarantees and making such free internal switches needs to based on a good understanding of the fund, market conditions, fees etc. A Good IFA can help there for a cost. There is also a lot of info online if you are brave enough and have time to get to grip with it all.
Other things to consider are the options each provider gives you at retirement. Traditionally the fund is used to buy annuities. Make sure your providers have an Open market option allowing you to buy an annuity from any provider (not just them) on retirement, most do. Also find out about phased draw down options.
I'm guessing these are 3 private plans (not ex company final salary defined benefit schemes).
Anyway that's just my 2p worth FWIW.
I suggest...educate yourself about your plans, read the blurb and understand it. Decide what your aims are in terms of returns and risk you are prepared to take to get them. Then source a good IFA, and agree a fee for their services in advance. The greater your fund value/contributions the better the value vs. fee will be for you.