I had this issue with my DS, keyless entry stopped working one morning, only worked if I kept the fob right next to the handle. I brought it to service and they were able to fix it with "keyless vehicle module software upgrade".
Thanks for the responses on the keyless entry. They ended up changing out the entire module and not just the module software. They said that LR would be issuing a bulletin on DS and Evoques as they have been seeing this issue.