The courts have at times used conventions to understand the effects of the legislation or understand unwritten aspects of legislation. They have, at times, used convention to enforce the relationship between the cabinet and the House of Commons, so that you can deal with someone as a cabinet minister through legislation that deals with them as a member of the House of Commons because of the convention of responsible government.
They have, at times, used convention to understand and make judgments about the constitutionality of legislation. There are limits to what they do with that, definitely. What they are concerned with is the effect of legislation to a significant extent, and where conventions can help understand the effects of the legislation, then they will bring them into consideration.