Thanks you for getting back to me so quickly.
I will let you know the details asap, im contacting my sister now.
I do know that the letting agency advised them about the owners selling early this year possibly Feb/Mar (will confirm asap) and they were given until May to move out. Which they did as well as fully redecorating the property and handing the keys back in on time.
The letting agency were indeed informed that they we moving out. They then informed my sister that the owners we no longer moving....(it seems a mistake was made my the letting agency as the owner did not want to sell and were happy for my sister to remain renting their property) however by this time my sister had already signed paperwork for a new property.
My sister has informed me that a formal complaint was made following many attempts to contact the letting agency who seemed to be ignoring them and would never reply back, she is currently making a complaint to the ombudsman for estate agents.
This whole matter has been very distressing as she has a small baby and this whole situation could potentially been avoided as she loved the first property and would have been more than happy to remain there.
I will get confirmation of the dates etc as soon as I can.