Not sure if I qualify as a 'new style ESA claimant' as I've been on it since it took over from Incapacity Benefit. Can't remember how long it's been to be honest.
The advice I was given regarding Universal Credit and trusts: if the Trust is correctly set up in the will before the person dies then it may be ignored - but it depends very much on exactly how the Trust is written. Regular income from a discretionary trust is deducted from UC, the capital may be ignored. BUT if the trust is set up by a deed of variation after the person has died the money in the trust will be treated as deprivation of capital.