If the Scotsure warranty that you refer to is the Insurance warranty provided by the SMTA then I would not be to hasty in flushing it down the loo.
There warranties are one of the best that money can buy and there customer service is totally beyond reproach.
No matter what insurance warranty that you have, wear and tear will not be covered as it is a mechanical failure policy, however if the gearbox was stripped down and a part was found to be broken then your claim should be successful.
Heated debates will never work in your favour in a situation like this.
Alex.