It is important to consider the downsides of selling your endowment policy such as:-

• Loss of life and/or critical illness cover
• Loss of future potential capital benefits at maturity
• The longer you keep your policy the higher the amount you could borrow from the life office or a bank
• Loss of potential windfall benefits if the policy is with a mutual life office who subsequently de mutualise

All of the above points also apply should you decide to surrender your endowment policy back to the life office.  If in doubt seek Independent Financial Advice.