Boycott Addison Lee

More that its not illegal, rightness and wrongness are more subjective. Many would consider an ISA (with limits on how much you can deposit) to be different to many of the methods being used by others to avoid paying tax.

Indeed. The tax benefits of ISAs, pensions and ride-to-work are deliberate incentives, intended to encourage socially desirable behaviour. Not quite the same as the legal loopholes that most would describe as avoidance.