Thanks Phil H, Yellow Sun and FlapsOne,
Appreciate your help. This question came around whilst having of a couple of beers with a friend. He was fairly insistent that reverse thrust accounts for more than 50% of the braking action on a typical landing roll. I was sure it was much less than this, say 20% or so. I was of the impression that whilst the noise is impressive, the brakes were by far the major factor in slowing the aircraft to taxi speed (under normal, non time constrained turnarounds). From what I have read (graphs and the like) it isn't too easy to work out a rough percentage of brakes vs reverse thrust under any preset (autobrake, etc) braking conditions.
I can well understand that this question is odd in that I am asking for percentages when there isn't one answer, but that's us non-pilots for you!!
I also realise that I've probably not managed to clarify my question at all and for that I apologise.