Actually I think you might have a case. BUT you are going to have to obtain some legal advice from an employment law specialist. You could try phoning the ACAS helpline to see if they can help you with your query, before you go to the expense of seeing a solicitor.
http://www.acas.org.uk/index.aspx?articleid=1410
My thoughts are that the company were aware that the IT work was in the process of being outsourced and therefore they should have excercised a duty of care to protect staff looking to move department.
You need advice from someone who deals with employment law and who is aware of legal/tribunal cases that have been brought in similar circumstances.
What you should not do, is accept the companies word for it that everything is above board and legal. It is worth the effort and maybe some expense in making sure any legal rights you may have are protected.