Hi Simon.
You could try the 'Klink & Dink' style, Tie on a dry Klinkhammer, then tie on, New Zealand style, beyond the dry fly, a small Mary, or similar tiny gold bead hairs ear nymphy thing, I like a bit of pink wool near the head for Grayling. Cast upstream and watch the dry Klinkhammer, if it moves or dips, lift immediately, Grayling can take off the top or underneath, this covers both options. Just get the depth right for the nymph.
I used to fish the Dee near Bala through a farmers field when I was 14 (40 years ago!, I know, old git

) there were some clonking fish about then. In those far off days, I used red tags fished in a team of 3, down & across..ah the memories

.