For the past couple of seasons Grafham has been difficult to beat for buzzer fishing in May, apart from maybe Draycote. Anywhere along the west shore should have good hatches of large buzzer.
If you can get there really early, swim out to Savages and put your towel down to reserve an anchoring spot.
If you want to use a little more skill and drift, then forget Grafham at that time of year. Go to the main basin at Rutland where anchoring is banned and you can do a bit of numpty-free drifting.
(Dons tin hat and hides behind sofa)
Graham