The answer is yes, but in doing so you would lose next years flowers.

Ok, I can live with that. Can I prune now? And if so is there a particular way of doing so. Thank you.

The surrounding plants are the main issue, it looks like it is straining for the light, have you a large hedge behind the hydrangea?, all the plants may need to be trimmed a little that surround it otherwise the same situation will arise again once you have pruned the hydrangea.

You can prune it now same as any other shrub. Take it back to an obvious bud facing in the direction you want it to grow.
Agree that you also need to address the reason for it growing the way it is at the same time.
You could actually move the shrub if need be.

Thank you all. Will prune accordingly. Have created space on one side which was the issue. Hedge and mature trees are all going to be cut back next month when I get a chap comes to help me with his power tools.

But if you do prune now there's a strong change you'll remove some of next years flower buds. I reckon you need to remove the cause. If it gets good light all round it will straighten itself up if you are patient. Otherwise it will just happen again.If you do want to remove some of the growth on the flowering side I'd wait until after the last frosts next spring, and try not to take too much off or you could end up with no flowers next year.

Thank you Yorkslass