Here's the e-mail address:
subscriptions@sagepub.co.uk
And here's the reply I received:
'We request you to please confirm if this will be an institutional order or an individual order.
Also please help us with order details (Volume and issue number) and address for a correct price to be quoted.
We will help you with the instructions to send your order request.'
So if you simply send them an e-mail stating that you are a private individual and would like to order a copy (or copies) of:
The Journal of Health Psychology,
Volume 22 Number 9 August 2017
Special Issue
The PACE trial.
And give them your address, they will tell you what to do next.