Putting my pedantic hat on, I have to correct the title of your thread. An AVC is an Additional Voluntary Contribution that is made to an occupational pension scheme ie paying more in than is required under the scheme rules. As you are self employed, it does not apply (it matters to ensure you invest in the correct pension product).
Anyway, back to your question, the amc of 0.75% is decent enough. You need to find out from your provider if you made a single premium top up, how much of that would actually be invested. Also, as you have such an old plan, are there any initial units... this is from the days when advisors took 60% commission. The insurance company had to make this back, so the plans had incredibly high management fees for a number of years, 5.5% per annum is the highest I've seen. The thing is, any new premiums also pay out high commissions (will be lower now due to your age) and any new premiums may get caught.
Where is your money invested? You may have invested in a poorly performing fund or moved it around. Usually when I see a 20 year old pension plan, the returns are pretty good. Another reason is that the charges might be pretty high. If you are only putting in a small amount, you may be having only 94% - 95% of your premium invested.
Steven
http://www.bluewaterfp.ie (www.bluewaterfp.ie)