Inheritance tax & trusts

My brothers and I set up a trust to deal with the excess amount that would have taken our mother's wealth over the inheritance tax liability level 2 years ago, as advised at the time. About £75K. With the changes bought in that gives her £600K to play with, we no longer need the trust. Two questions: Should we leave the trust standing, even though it means paying 40% tax rather than the 20% in a bank account? Are there any benefits? If we dissolve the trust and split the money, will we have to pay any tax on it? (assuming that mother will be living another seven years)