The Queen is wearing the sash and star of a Grand Cross of the Order of the White Eagle - the highest Polish decoration conferred on foreigners. Her Majesty received this order in March 1996 during her state visit to Poland.
The tiara is known as "the Grand Duchess Vladimir tiara", and was bought by Queen Mary from the exiled Grand Duchess in the early 1920s. It consists of diaomnds in circles, with a pearl-drop hanging from each circle. The Queen is also wearing a diamond and pearl necklace, a gift to Queen Victoria on the 60th anniversary of her reign from the people of the UK; and a diamond brooch originally given to Queen Mary as a wedding-gift.
The Duke of Edinburgh is wearing the sash and star of the same Polish Order, which I believe he also received during the 1996 state visit. His Royal Highnes also wears the neck-badge of the British Order of St Michael and St George, of which he is Grand Master.
The President of Poland is wearing the sash and star of a Grand Cross of the Order of the Bath - the British Order usually given to republican Heads of State - which he received during the 1996 state visit of Queen Elizabeth to Poland. His Excellency is also wearing the star of a Knight Grand Cross of the Order of St Michael and St George which he received during an official visit to the UK in Oct 1996.
It seems the President of Poland did not get any new decoration for this visit (there were no higher decoration to give him).
Mrs Kwasniewska did not receieve any British decoration. Neither does she have any Polish decoration.