Wills have been known not to be found and they can sometimes bring out the worst in families and friends, If the will has been found and has gone to probate (which confirms the executor’s power to administer the estate) a copy can be obtained, from I believe the postal searches Dept in Leeds, rather than York, the cost is around £6.
The testator must have been acting of his own free will and not under duress or undue influence of any other person, if you do not believe this was not the case I suggest you take advice before proceeding.