Yup, only other option you really have then is, as you suggest, where the basin waste elbows down, take out the bend and put in a tee with a 32mm AAV in it.
As mentioned above though AAV's shouldn't really be added to fix a problem and only really used in instances where the design specifically calls for them, that and ideally they should be installed at a point higher than the spillover level of the highest fitting they are connected to, i.e. your basin (which you may find difficult)
As mentioned above though AAV's shouldn't really be added to fix a problem and only really used in instances where the design specifically calls for them, that and ideally they should be installed at a point higher than the spillover level of the highest fitting they are connected to, i.e. your basin (which you may find difficult)
