As a council tax payer, then so are you.
Besides they are doing nothing illegal unless government change the rules and there is no chance of any government doing so, especially in these post-Brexit times when Britain is Open For Business.
In any case if we all stopped supporting businesses that avoided paying as much tax as possible we'd have no iPhones or Android phones and all those painfully earnest, beardy hipsters (who so tragically fail to realise that they are no longer trendy) would have nowhere to sip their Latte and opine about the gap between rich and poor as they text on their £700 iPhones or gaze at their £400 square smart watches.