I think the Form 8822 is only for US residents. If you normally submit W-8BEN forms for agencies, the only way to change details is to phone the IRS in business hours. I've done this a couple of times and the International Taxpayer Service Call Center are very helpful. Ring +1 267-941-1000 and they should sort you out. Waiting times are very short.
If you just submit a new W-8BEN to an agency with your new address it will be rejected if it doesn't match IRS records.
HTH,
Colin