Legally, it doesn't matter if Canon offer a warranty on their product.
You didn't buy the camera from Canon, you bought it from Kerso, and as such, it is Kerso that your contract is with. The contract being that you provide the money and he provides the agreed item that is fit for purpose.
The SOGA states that if the item becomes faulty within a reasonable period of time (it doesnt define this), then the item must be repaired or replaced without significant inconvenience to the customer. The decision to repair or replace is at the retailers discretion (in this case, Kerso).
Some retailers like Argos are happy to replace the item even many months after purchase, if it becomes faulty. They don't *have* to do it, but they do.
So legally, you can force Kerso to accept the camera back for repair or replacement (which one will be his choice).
However, I can see why Kerso is directing you to Canon.
If you were to use the SOGA and return the camera to him, he would then choose to get it repaired, and would do so using the manufacturers warranty, by sending it back to Canon.
They will then repair it, and send it back to him...and he will send it back to you.
Which means even longer without your camera, so it makes sense for him to instruct you to deal with Canon yourself.
As it stands you WILL be getting a working camera back, regardless of how Canon react.
The problem we face as consumers is that high street retailers use this system as a way of saying "not my problem...go to the manufacturer" and *that's* where the SOGA works its magic. Kerso isn't doing that here.
So while you have the option of saying to kerso "I don't care...take it back and sort it", it would end up taking longer for you, and therefore would be cutting your nose off to spite your face, so to speak.
You have the right to have it repaired for free under the Canon warranty, this is the quickest option available to you.
Kerso *could* give you a brand new camera, and send yours away for Canon to repair, but that would just be silly business sense IMO, he would then end up with a used (albeit repaired) camera, which is worth less than the new one he's just given you, if that makes sense.
I would complain about Canon too. I have had problems with them myself today
Hope you get a working camera back soon!