After a whole year of wrangling with Marshall I was helped by a lady who told me that the local Marshall agents would not repair the speaker without the receipt. I said I was prepared to pay for the repair, but I just wanted the speaker fixed. She gave me the name of "a company" in China, and also the address. She then said I would have to pay for the shipping costs myself, which would roughly be equivalent to half of what I originally paid for it. I can't afford to do this. Plus, this is just an electrical item repair centre, and as far as I know they are not the official Marshall agent, so I wouldn't be confident sending it anyway.
I then said I would seek legal advice in an effort to resolve the issue. The reply I received was, "please remove the negative comments you have made on social media regarding Marshall'S lacklustre post-purchase and support" Marshall have a new guy in charge, and I believe that this person must be from an accounting background, as Marshall CS's used to be very robust and reliable. Now, I wouldn't trust Marshall with an odd sock. Neither will I ever, EVER purchase any products from them - be it a speaker or amplifier or whatever.
I am finished with them.
Best of luck, I think you will need it!