Go and have a chat with the Head of Training or Chief Instructor and express yuor concerns. Weather and aircraft serviceability can't be helped but instructor availability can. There needs to be a fixed timetable when your instructor is available to teach you' if that coincides with bad weather, then I'm afraid that's unfortunate but if other students are getting priority or he can't stick to the timestable, then there's an issue which needs to be addressed by someone more senior.
After that, if things don't improve, then yes, move on. Having large gaps (i.e. you're only flying once a month on avergae!!) will hinder your progress and it would possibly take you more hours learning that way.
Cheers
Whirls