Hi All,
Just to keep you updated on this, Bridgestone paid 50% towards the cost and we Teesside contributed the rest (the least that we could do under the circumstance).
We understand they do have a problem with this, but it seems it is more the exception then the rule.
Our advice if you are having a problem is to contact your tyre supplier or Lexus dealer if that's where you purchased them from , the down side is they will probaly have to remove the tyres and then send them off for inspection, and you are not guranteed that they will help towards the cost of replacement. it will greatly depend on the level of remaining tread.