OP, this is a website based mainly on Irish issues. Saying all this, it does appear that you are going to have to use the services of a fairly large legal firm (solicitors) who would act on your behalf. Be prepared legal work in this regard will cost you quite a bit of money, but as the beneficiary of a will, and if there are any funds there, the costs should be liable from the estate of your grandfather.
However, saying all this the fact that it is a trust in the Isle of Man, makes matter considerably more difficult, where issues are kept relatively confidential and private.