A I support your governors' decision. I know that the School Teachers' Pay Review Body has, once again, strongly pressed its view that teacher governors should not be involved in heads' and deputies' pay, though I think they accept that it is not illegal.
In my view, arguments about the propriety of teacher governors' involvement in this aspect of governors' work are no different from those which apply to other "close to home" duties of governors, including teachers' pay, discipline and grievance, and appointments. Indeed, they seem to me in principle the same arguments as apply to their involvement in determining school policies outside the personnel field, which at their level as teachers they would probably not share in.
Once you decide that teachers are to be represented on the governing body,you surely grant them the same status and expect from them compliance with the same rules (for instance the need to withdraw from a decision they might individually profit from) as others.
I don't think governing bodies would work well if any group were second- class citizens or if one couldn't draw a clear distinction between teachers' status as governors and their status in the workplace. I do not know how the Department for Education and Employment would answer your question, but it is to me significant that, following a legal case on appointments which involved the National Union of Teachers and Croydon council, the words "greater than the generality of teachers" were inserted in the regulation about declaring an interest. I have always assumed a connection.
I am not even sure that a governing body coming to the opposite conclusion to your governing body would be acting legally, though this has not been tested in the courts. It is true that the governing body might have a discretion to decide whether a particular teacher governor had a special interest in an individual issue, but that is very different from ruling against teacher governor involvement in principle when the law does not.