The medical instruction is sent to evry applicant and in that letter it CLEARLY TELLS APPLICANTS where the
doctor MUST send the medical result so why do you or your doctor can chnage the rule? Obviously, if the doctor
sends it to canada, your visa office in london will still receive it but only God knows when. Why did you not show
the doctor your medical letter for him to read it clearly where he should send the result to? He would have assumed your visa office is in america as most of the applicants he deals with are from there. Better go to him with your medical instruction letter and request him to send it to LONDON.
This is what your visa office told you to do, why is the doctor doing something different?
I know of someone, principal applicant was in london, visa office was in london but wife was in nigeria. The wife did her medicals in zhankli hospital, abuja. The doctor said he would send the result to ACCRA-ghana! But the medical instruction says he must send the result to london. The principal applicant had to scan the medical letter instruction to the wife, the wife printed it, shown it to the doctor then the doctor agrred to send the result to london. It took just 2weeks for the london office to get back to the principal applicant to submit passports (for both principal applicant and wife) because they have received both the medical results on time. I hope you understand all my illustration! Don't risk waiting for 6 to 12 months and sleeplessness! Call your doctor, give him the london address to send your result to as instructed by your visa office.
Good luck