Wendy,
Sorry, I should have explained
:
Like Sandy said, the rivers vary in character and as such, contain different types of flies. It also depends where about on the river you are...upper, mid or lower reaches as the fly life can vary as well. For example, Chalkstreams tend to have a big hatch of large Mayflies and so at certain times, the only fly you need is a big old mayfly immitation.
The list he has given you is, as always, spot on
I think I would add to that some leaded caddis imitations, stonefly nymphs and possibly something "Shrimpy" for fishing in tumbling, streamy water.