Because we've had a wet year, the Hydrangeas in this part of Surrey are looking fantastic.
The colour of the flower will depend on the soil,whether it is acid or alkaline, and whether it has aluminium ions that the plant can take up. Generally a soil pH of 5.5 or less will be able to keep Blue flowers blue. - Soil pH's above that will go pink. There are some trace element products that you can add to the soil to help the take up of the Aluminium Ions. I havn't found them to work in the long term, and here in Horsley, where most soil are neutral, - pink, white and slightly purple Hydrangeas are the order of the day.
You don't need to prune off the flower heads until well into spring, because they protect the new growth, so I always wait until Wisley have pruned their Hillside Paniculata, in April, before I get out the secateurs.
After admiring clients Hydrangeas for years, I decided to take the plunge myself last year. - I'll need to water them well in my soil, - but they don't mind some shade, so this Hydrangea Annebelle, is doing wonderfully under my front garden Magnolia. This was grown from a 9cm mail order plant last year.