First and foremost, Giles and Mary should update their wills
Looking into the options surrounding power of attorney will give some peace of mind
If there are concerns about the investment strategy and/or recent performance it might be sensible to ask a discretionary manager to review the portfolio and discuss the options thereafter, as looking after a portfolio oneself is time consuming
It is worth considering an inheritance tax mitigating portfolio service – as experienced investors they might be comfortable with the risks whilst keeping the portfolio outside of their estate for inheritance tax purposes