It is a highly polished tile, I would have thought it was the opposite.
A highly polished tile has a glass like finish so it would be like trying to seal glass. The seal has nowere to absorb into? I have poured a bit of seal onto the tile and it justs puddles.
regular pocelain tiles are very hard wearing and not pourous at all, and therefore need no sealing.
A highly polished tile has had the top layers taken off during the polishing process and the pores (for want of a better word) of the tile have been opened up.
You will need to seal your tiles if they are highly polished, FILA is a popular sealer, but just ask at any tile store and they should find you the right product.
Are the tiles definetely porcelain..?
Did you get them from B and Q....?
How are you applying the sealer...?