Trust compensation

In 1985 I received a payment of £5k from a trust which had been administered by a bank trust company. In 2015 the company wrote to me advising that I had been "disadvantaged as a life tenant and a remainder man of the trust" and as such I was entitled to compensation. According to them the fees for acting as trustee from 1966 to 1985 were calculated using the wrong fee scales. They then paid me a further £1700 which they advised was the income and capital compensation due as a result of this error. While I was very happy to receive the £1700 I have no idea whether or not it was reasonable compensation or if I should have challenged it? Hoping for some guidance if anyone has knowledge in this area.
Thanks