I think Drake's is fabulous. Customer service is excellent and they have a nicely balanced range including traditional and slightly more modern patterns. I know that your local Zegna store would also do MTM ties but Drake's would be my first call.
I've heard tell of people getting it done in Harrods but the price at £200+ per tie seems rather excessive! I don't know any more details on what is offered.
On the Internet / Mail Order front, it must be worth mentioning Sam Hober. Truly bespoke IMO and good value.