This is a question very close to my heart at the moment ... how much do I need in order to retire. We had a preparation for retirement seminar a while back which tried to get to grips with the topic
They suggested that spending in retirement tends to be 'u' shaped, an initial high level for the holiday of a lifetime or work on the house, then costs dropping back to normal only to rise in much later life with costs for card etc.
The Provision that is required for whatever is thus divided into
the basic costs of living ( utilities, insurance, car etc)
Treats such as holidays, family events and whatever else you choose.
It's less easy to make provision for later years.
The post will need to finance these. Some form of annuity (or other, defined benefit pension ) is probably required for the basic costs and the rest can be financed by drawn down of capital.
A spreadsheet makes it very easy to Model out what these might cost over a range of number of years. You can also adjust what counts as basic costs (Netflix, Amazon prime etc) and what would be you 'budget' for variable costs such as travel.
Hope that helps somewhat. It's seems lovely to have an IFA to just tell you what you need, they will only be guessing....