Birmingham council is run by Labour but Westminster is run by the Conservatives. Unless by classes you mean all politicians, it's not the case that it's all linked back to central government.
Besides, corruption isn't needed to explain this. ERP projects fail all the time, with SAP as well.
Doesn't really make sense to say that politicians are structurally in power in Westminster though. I mean, yeah, kind of by definition in a democracy the political classes are structurally in power.
Not in the way that we have in the UK - where most representatives (regardless of party) have gone through the same schools and the same social circles (bit of journalism, bit of finance, all largely in London or surrounding areas).
I know so little about British politics that I take Yes, (Prime) Minister at face value. I would have thought it war more about the (benefits and) interests of bureaucracy and civil service.
Besides, corruption isn't needed to explain this. ERP projects fail all the time, with SAP as well.