most diy outlets sell Silicon eater, follow instructions on tube , this will do your job.. and yes trade tiler does sell it , but you will have to pay p&p so just use b&q or similar....
i cant remember the name of the tool but its like a big stanley blade with a handle, top drawer for taking Silicon off a tile, and the blade wont scratch the tile if its gloss finished, a matt finish may cause different problems and id prob go with the HG Silicon remover.