A full sized garden fork and a lot of elbow grease, I'm afraid. Shouldn't be too difficult if they're only 3 feet high, the root spread will have been restricted by the topgrowth restriction.

If you cannot do it yourself, get someone who knows what they are doing. Take out a trench at one end, deep enough to dig under the roots with a fork. Work away the soil until it's free, if the shrubs are in a row continue with the next one.

Thanks. I might start in the good weather today and see how it goes.