How best to colour bright red hair to chestnut?

[nobodysfool]

I have been dying my hair bright red for years and the constant dying has taken it's toll on the ends as they are getting quite damaged and dryer. I have tried all sorts of conditioners which have helped a little but I have made the decision to go back to a colour nearer my natural hair (whatever that is) to give it a bit of a rest. The only time it looks ok (see attached pic) is when I straighten it - which is a vicious circle.
I have let the red fade quite a bit but am concerned about a chestnut going too dark over the red base.
Any advice?

[nobodysfool]

anybody?