Big question Cruiser - it depends what you mean by "protection". If you simply mean what happens if the Prudential goes bust, then the Financial Compensation Scheme would step in - and (at least theoretically) you would get back 100% of the first £2,000 and 90% of the balance - unlimited. Quite how that would work in practice, i dont think, has never been tested. It's worth bearing in mind though that if The Prudential goes bust, it really will be a case of "will the last investor to leave England, please turn out the lights!" http://www.fscs.org.uk/consumer/key_facts/Limitations_of_the_scheme/Compensation_Limits/
If you mean, are you protected against the fund falling in value - no you're not. If you mean are you protected against annuity rates falling so you end up with a smaller annuity than you would have if you took it now - no you're not. You really ought to be taking advice. Go to http://www.findanadviser.org/faa.aspx and find a Chartered Financial Planner and have a chat - it shouldnt cost much, and if it does it will be money well spent.
Marc Ruse CFP