Maybe it is your turn to try a nice fine fly on a small hook?
I'm living in the south-eastern corner of Poland - a hilly land with the magic blue ribbon of the San river running through it. The San river is one of the best shelters for grayling in Europe, it is also very often a place of huge frustration of anglers coming to catch these fish.
The reason is very simple - what hangs out of a typical British fly box is rather a reason to laugh for a Polish grayling, than a nicely looking snack. Not that the English flies are ugly (except for blobs) - they are just not adapted to our conditions and insects.
I don't have the knowledge to state if our insects are smaller than yours, or if the species of invertebrates vary so much between locations. The fact is - we fish way smaller flies with very sparse bodies, very often made just of thread and single cdc plume. It is also nothing unusual for us to use size 20 and smaller flies - both nymphs and dries.
My personal theory is that grayling focus on flies that hatch in big quantities and as on the San the most massive hatches are of flies size 18-22 that's what the fish most eagerly take. That's probably why very often on my river you will see big meaty mayflies going down not being even looked at by the fish.
The only exception - and the subject of an eternal quarrel between me and Jeremy Lucas - is the sedge. I've been catching grayling during massive hatches of duns on a sedge that didn't hatch at the moment. Why? Maybe because catching fish on a dun requires a perfect imitation and then you need to be lucky - why should a fish pick your poor, pretend-to-be, dun when there is 500,000 natural flies around? But when among these countless duns you put a nice juicy sedge the fish will say - "Hey, I know that guy, he tastes quite well, I've been eating these all summer! "
One other thing works my mind that could possibly have influenced local fly tying - the poverty. Poland was a funny country, where buying fly fishing gear wasn't possible some 20-30 years ago, especially in a lost town like Lesko. Not only I mean there wasn't a single fly fishing shop, but also a good rod and reel was worth more than an average annual salary in the 80's. Same situation with fly tying materials: who could buy a spool of fly tying thread for 1 $, when an average monthly salary was around 15$? As explained by my friend Adam Skrechota - one of the first in fly tying business in Poland - fly tying in the 70's and 80's was about chasing cocks and hens in the garden, pulling threads out of carpets and clothes, and drilling holes in bait hooks by watchmakers. Would you use these preciously gathered materials in big quantities?
Beautiful in its simplicity, efficient, fine - that's a typical fly box contents of a Polish angler fishing the San river. You won't see a pink Klink size 8 in our boxes, you won't find a triple tungsten bead nymph, you won't find a boobie either. And still we catch fish. I see no reason this wouldn't work on your river for grayling.
A lot of my friends used our flies on their home waters with success, Pat Stevens included tying of fine dries and nymphs in his demonstration programme, Jeremy Lucas says: all the fish in a river can be caught on a single CDC dry fly in the 17-21 size range, John Tyzack and his top secret Polish Sedge causes a regular ecstasy among trout and grayling wherever he goes. John Philbrick from Australia proudly uses our flies to catch some trout on the other side of the globe.
Maybe it is your turn to try a nice fine fly on a small hook?