What is it?
 

I hate this plant. It's at the back of the garden amongst the hedge and bushes which were planted when we moved in. Every year it reappears, even though I cut it right down and it's always diseased. The nicest thing about it are the berries. The leaves always have holes in them right at the start of the season, ie early spring and, in some years passed, by the summer the leaves are nearly all eaten away. I chop it right back, but it is persistent in making a reappearance. What is it?

Guelder rose (Viburnum opulus). If you cut it back less you might notice the flowers more!

I cut it back because the leaves are always so eaten away. I don't know what eats it because the other plants around it are fine.

Yeah, its a bit of a wild plant so it will never be neat and tidy. You could try giving it a little more shade and less root competition for water from other shrubs (Leaves are a shade red) and it may be more healthy looking and in a better position to recover from insect damage. Best in partial shade I reckon anyway for ornamental purposes.