Not gonna buy it but what's the name of that shop that you've sent your RM in London? Knowing that it is London and RM is from Switzerland, they could verify that easy with tools that they have. What if they just did some inspection and then able to replace some parts of it? you're unsure with this kind of process that's why bringing it with yourself into a shop or company that checks it is a must. The watch era is starting to come back, try to search for those shops that are in social media that is into this business. Save some money of flight ticket and go there like in Dubai and have a personal visit once they have agreed to your pricing and validates its authenticity.
It is called Cudoni. A luxury goods and accessories selling marketplace. They closed down but I think their stock went to another company. I have the emails if you like. Thanks for looking at my post and then replying.