Ringing for specific church events I can the answer I expected - hubs are a good way to maintain ringing both for routine services and practices since bringing ringers together can achieve critical mass. However, there it is still the imperative that we recruit more ringers, not least to enable ringing for major events like Harvest, Christmas, Remembrance and national occasions.
The advantage of hubs for recruiting is that they should appear to be active and lively groups able of fostering ringing. Having said that, hubs still need capable teachers and facilities, both for the initial stages and advancement. Recruits to such hubs also need to be willing to travel to other towers when required.
So forming hubs / clusters (whatever they may be called) in name only is not sufficient - training aids, teachers and recruitment have to be an integral part of forming a hub.