Endowment Policy Value

I have a 25yr endowment policy taken out with Sun Alliance ultimately renamed as Phoenix Life. This policy should have paid out £55k+ based on the sales spiel at the time. We all know what has happened since that time! It is actually worth £31k+.
Phoenix wrote to me in January with a value and to tell me that they would send a cheque out to me in March, when it matured. For various personal reasons I didn't chase them up when the cheque didn't arrive. In September they wrote to me again saying I needed to take action and asking for a letter with all my bank details. I asked, as they had had my money for a further 6 months, what the final value was. It had gained £65 which roughly works out at .002% interest over 6 months!
I have just asked them to send me the cheque, as originally promised, which I've been told will take 5 days and I was then asked if I would like to speak to an advisor for advice on what to do next..... brass neck or what!