You are receiving all communications via e-mail, right? Until the Passport request (since you are visa exempt, they may not ask actual passport but a scanned copy), they may send all communique via e-mail anyway. Also, you can have the mailing address changed to your spouse's mailing address in Canada by writing London visa office. Many people who have out-land visa office use Canadian spouse's mailing address anyway, so that no mail is lost. I don't see why you have to notify CIC about this 6 months visit when you can just do a change of mailing address.