Here are a couple of ties from my favourite tier Rene Harrop. Not sure how well known he is over in the UK.
These patterns are deadly over here on my local rivers in Canada. These are tied to represent one of our early mayfly hatches a hendrickson, but these patterns can easily be adapted for any mayfly hatch.
Last Chance Cripple

Hook: Any Dry (Hanak H130BL)
Thread: Yellow
Tail: 3 Lemon Wood Duck
2nd Tail: Antron Dubbing rolled; 1/2 length of wood duck
Body: turkey or goose biot
Thorax: Dry Fly Dubbing
Wing: Dun CDC; two feathers with curves facing out
Hackle: Grizzly
Polywing Dun - a modification to his Hairwing Dun
Hook: Any Dry (Hanak H130BL)
Thread: Yellow
Tail: Coq De Leon
Body: turkey or goose biot
Thorax: Dry Fly Dubbing
Wing: Aero Wing or Poly Yarn
Hackle: Grizzly; spread underneath to sides then trim V
Emerging Dun - Screwed up the head but youget the idea

Hook: Any Dry (Hanak H130BL)
Thread: Yellow
Tail: 3 Lemon Wood Duck
2nd Tail: Antron Dubbing rolled; 1/2 length of wood duck
Body: turkey or goose biot
Thorax: Dry Fly Dubbing
Wing: Dun CDC; 1/2 to 2/3 length of body
Throat: Partridge
A better version
Any comments to improve the ties always welcome.