Yes. the conifers will have removed all goodness from the soil so working in organic matter from compost or well rotted manure will help revitalise it. Mycrorhizal granules work when in contact with the roots of the new plants so scatter them on the roots of the red robin as you plant them. Make sure they're watered well before planting if in pots or, if bare rooted, soak them in a bucket of tepid water for at least an hour before planting. Bare root tends to be chepaer than potted plants.
October is an excellent time to plant as the soil is warm enough to encoruage root growth and there's enough rain around usually fo rit only to need watering at the time of planting. Once planted and watered give them a good mulch of compost, well rotted manure to retain moisture. The worms will work it iin for you over the winter.
Next spring, give them a good general feed of either pelelted chicken manure or blood, fish and bone and mulch again if you can. They should then get away well and provide a lovely hedge for years and years to come.