Welcome to Goy. Climbing hydrangeas are usually sold in the pots they were grown in so you can plant at any time of year as long as the ground is not frozen. When planting shrubs I mix some bonemeal in to the soil to help encourage new roots.

Thank you Scotsgran x

Can I just add, do mix the bonemeal well into the soil before planting - if too much touches the roots directly it can kill them, as I discovered to my cost!

You are right Steragram. I dig the hole 2 x the size of the pot the plant is in. I sprinkle bone meal on foot and sides of the excavated hole and fork it in to the foot of the space. I backfill with some fresh compost and the soil I took out.

Brilliant. Thanks x