I have just sold my mobile home in Spain using an English agent with a UK based limited company, when the home went up for sale in July 2015 the agents fee was £1,250. I accepted an offer on 31st Jan 2016 & the following day received a copy of the company's new terms & conditions which stated that as of 1st Feb 2015 the fee would be £1,250 plus VAT. Is this legal?