Contract law question (UK), based on remedies

On 14 July 2011 Orlando agreed to buy "The Billiard Table", a painting by Georges Braque, for 200,000 from The Gallery. The painting was to be the centrepiece of a new exhibition that Orlando was staging in his art gallery in Manchester in February 2012. He arranges for brochures and posters to be printed as well as advertising the exhibition in magazines.Meanwhile there was a very popular exhibition of paintings by Braque at the Royal Academy and prices for his paintings trebled. In November 2011, before the date for the delivery of the painting to Orlando, The Gallery accepted an offer for the painting of 650,000 from Henri.

Advise Orlando as to any possible legal and equitable remedies