I presume you were, or think you were, mis-sold the insurance?
You have 3 years from the time you can reasonably be expected to realise you were mis-sold the insurance. (which is somewhat vague!)
Your best bet is probably to try and see what they say, but as the insurance was taken out before the regulations covering PPI was introduced in 2005 your claim will be looked at based on the codes that were in place at the time from the insurance and banking industry and not under the 2005 regulations.