That sounds about right OF, so if you have say, 4 door-to-door items for the week, and given that a typical *walk is 500+ delivery points, that amounts to at least £20 per week.
The number of leaflets to be delivered can vary quite a bit, as they seem to be targeted according to postcode, so if you work in a smarter residential area you get more of the stuff, so I can understand the opposition to a flat fee.
*a postie's delivery round is called a 'walk' regardless of whether he walks, rides a bike, or drives a van to get his job done