David Austin's website has a section about deterring rabbits from eating roses. This is what he says: "The best way to exclude rabbits is a rabbit proof fence around the rose garden using 36”/1m wide chicken fencing that has the bottom 6”/15cm bent outwards and is buried to prevent tunnelling. There are various sprays that claim to keep rabbits away but their effectiveness depends on regular applications and the rabbits may start getting used to the taste."
A fence of chicken wire, which would need to run along both sides of your young hedge, would not be expensive.
An alternative to a spray would be to water the stems of the hedge with a solution of chilli powder. Watering the ground with chilli powder solution is a recommended way of deterring rodents from digging up bulbs.