We got £12850 off the endowment for our mortgage so over 20 years we got £53.50 a month back.
Take off the £1150 we owed and that turns out to be £45 month we got back.
That's muddled, the endowment is separate. You got back £53.50 in the end for every £20 you paid into it... that it didn't cover the full amount of the mortgage and you had another payment to fully cover the doesn't change the fact that you got that return.
If we had paid a 'normal' mortgage we would have nowhere near have paid an extra £45 a month on top of our £60 so we did OK, did make a bit of money back and didn't have a right to claim.
Some people however got totally ripped off.
A minority AFAIK, most people ended up with an endowment that did cover their mortgage. Some of those people perhaps shouldn't have had a case but were able to claim simply because the companies had lost the paperwork showing that the risks were highlighted. Taking a loss on a financial product (or not getting the return you expected) isn't in itself a good reason for compensation.
The compensation is just to people into the position they'd have been in had they instead taken out a repayment mortgage (so paying off the capital and reducing the interest on the loan over time) not to bring them up to whatever lump sum bonus amount they claim the salesperson promised, so it seems you've basically had 20 years of making lower payments than you'd have had to make to have been in that same position with a repayment mortgage.
The Dell Boy advisor may have promised unicorns to you that didn't materialise but you still made a return from the investment and were better off it seems.