Just to let those who helped us know our journey went well.We went to our local station and changed the time of our train for one 30 minutes earlier.Then as suggested we got our ticket ,from St Pancras to Gatwick which was a great time saver.Then as someone told us to cross road from Kings Cross to St Pancras,which we did. We arrived at Gatwick at 9 50 for check in at 9 10.Brilliant thanks for your help