Farleton is one of my favourite haunts, however I haven't visited recently. Ask Simon at the lodge for info on what's catching.
Top flies include Black spiders, Olive nymphs, Shipmans, Epoxy buzzers (Flashback buzzers are worth using; and I would also take some Olive and Black redheads), CDCs (I can guarantee that you'll catch on these when the fish are on the top), Blobs (use one of these with a floating line and a long-ish leader, then just leave it to drift) and Diawl bachs. Bibios and Bloodworm are also worth trying.
Generally speaking, anything small and dull should catch.
There's also a stream that runs parallel to the fishery and around the back, it contains plenty of small brownies. Again, ask Simon for the details.