If our level of consumption is unsustainably high, (and I've no idea whether the UK's is although I suspect it might be given the levels of consumption of 'luxury' items I see around me), then is an increase in debt the only cause or has income become unsustainably high too?

In that case, the prevailing economic forces determine how the balloon will pop, but not if.

Interesting stuff about the relative cost of workers' welfare though. There needs to be some form of welfare-offsetting, comparable to carbon-offsetting perhaps.