If you are fitting a SINK to a wall then our bathroom fitters tile drilling kit has a useful socket size at 30mm.
What you need to do is drill out a PLUG of tile so that your anchor bolt slips through.
(Above shown is a Fischer Fixing Kit slipping through a 16mm hole created by the 16mm tile drill in the pack)
Now take a look at this shot of a tile drilled out with the 30mm tile drill.
Obviously once the sink backs up against this hole then it will be permanently hidden.
The beauty of working with a 30mm hole in the tile is that it gives you room to access the material behind.
In your case its stud board plasterboard. In which case you can get a decent hollow wall anchor secured into the plaster quite easily.
http://www.NoLinksToThis/sfd/i/cat/03/p4075803_l.jpg
Hope that makes sense?
Note that the advice above showing the hollow wall bolt will ONLY WORK if the sink is a pedestal. Thats because of the weight of the unit. Its taken up by the pedestal.
If your basin is a HALF PEDESTAL then you will have to use a strong fischer anchor bolt.
Dont be hanging this sink with a couple of 8mm screws !
You will need a substantial frame and bolt to take the weight.
The bathroom fitters kit is a universal tile drilling solution for the installation of holes into tiles from 365Drills