Was the guy who sold you the endowment an Independant Financial Adviser or an Appointed Rep of the endowment company?

If he was an IFA then it's him you need to complain to.

If he was an A.R. then complain to the endowment company.

It's the advice you're complaining about, not the performance of the product.

When were you sold the policy?

You have to complain within 6 years of being sold it or 3 years after your first 'red' letter.

Also if you bought it in 88 or earlier you might not be able to claim anyway