Cats, not all gliding clubs or instructors are as dogmatic as you suggest. Many will allow the student pilot to choose the method of launching, though they may offer advice as to which is most suitable on the day for the stage that the student pilot is at.
Chris Reed beat me to it with what my advice would be for a PPL starting a conversion to gliding in the flatlands and winter, with no thermal or ridge soaring available.
Chris N.