I've been avidly following Bamford Watch Department (
http://www.bamfordwatchdepartment.com/) for some time on Instagram. They specialize in custom (or bespoke) watches and provide their own warranty. I've yet to purchase so I can't attest to the experience.
I used the "Customizer" to customize a Rolex and it seems the pricing isn't all that bad compared to the price of the watch to start with.
You can try the customizer here:
http://www.bamfordwatchdepartment.com/us/?page_id=10357