When you invest "with" a Life Assurance company (pension, savings, protection etc) you are not investing "in" the Life Assurance company. If its a pension plan, then your value is based on the holdings in the underlying assets you invested in (whether a Managed Fund, an Equity Fund etc). The assets in the various Funds are separate from the success or failure of the actual Life Assurance Company itself. That is how the unit-linked companies operate.
The only exception might be the Mutual With Profits companies (such as Equitable Life), but very few (if any) of these are left.