I use Casaron G weed killer. it comes in a granular form and is easy to shake around the base of the hedge. it will keep weeds and grass away for most of the year and won't effect the hedge.
Bought a plot with a derelict building at the beginning of the year. Do not intend to build on it for about 12 months. Today we got a letter from the Co Co - need to tidy up the gardens at front and sides. Mainly shrubs, weeds, flowers and a long type of grass. I intend to get the shrubs ets cut down completely. Will Roundup do the rest? And if so, for how long? Anyone got a better idea?