(1) If in proceedings for infringement of a patent it is found that any claim of the specification, being a claim in respect of which infringement is alleged, is valid, but that any other claim is invalid, the court may grant relief in respect of any valid claim which is infringed:
     Provided that the court shall not grant relief except by way of injunction save in the circumstances mentioned in sub-section (2).
     (2) Where the plaintiff proves that the invalid claim was framed in good faith and with reasonable skill and knowledge, the court shall grant relief in respect of any valid claim which is infringed subject to the discretion of the court as to costs and as to the date from which damages or an account of profits should be reckoned, and in exercising such discretion the court may take into consideration the conduct of the parties in inserting such invalid claims in the specification or permitting them to remain there.