Good fabric can be obtained trough e-bay, there is a good shop called British Fabrics.
Fit and the rest - look at bmulford and his suits or Matt Fan or iatmatt on the waywrn thread;
quality - working button holes on sleeves are not a real sign - the fit and construction are- go for at least 3 fittings, one basted, one with collar and sleeves, one final. In the first fitting you should be able to see the canvas, at least the lapels had to be basted by hand.
Good luck and...