Depends on where abouts you are, but try contacting any ABRS riding schools in your area. I did mine through PC years ago, and we went to the local Riding School.
Please contact your local BHS Road Safety Officer who is Mrs Anita Knagg anita.knagg@tiscali.co.uk Tel: 01254 888285. She will be able to advise you of the closest centre where you can take the Road Safety Course and Test.