There is a Mrs S J H Oliver who is on the AHS Disciplinary Steward List so I dont know if it would be the same person but it might be worth a try writing to her via the AHS.
Her address is on the current Judges List of the Arab Horse Society. I have a copy for work and my only worry is that I don't know how widely available it is as I don't like handing out people's personal details without their permission.
If you wish I will contact her with a copy of this and ask her whether she would mind me giving you her address or not.