Mis Bought Endowment

AdesSafe

about 20yrs ago we started an endowment, 10yrs later we had 25k in it but astill a long time to maturity, I was an engineer and left all financial decisions to my wife, as she worked in a bank...we were approached by a financial advisor who offered to find us a mortgage...we needed a deposit, he suggested we sell the endowment as he could get 15k for it.....we agreed (stupid I know) anyway we went through the process of moving, he comes back and says I cant get 15K for it, will you accept 7k.....reluctantly we agreed.....(are we stupid or what) anyway...recently Ive been thinking about this.....and thinking that I cant prove, that I didnt insist on the sale.....but........If I can show that at that time I could have (easily) got a better price....then Ive got him.....but am I out of time......
Ive spoken to other financial advisors about this and they say that guy is notorious in the industry for these sorts if rip offs.

how do I find out how much I COULD have sold or traded the policy for.....and perhaps more importantly, am I out of time....to pursue a case of
negligent advice,

it might also be interesting to see who bought or benefitted from the policy.....