Solution taken from another forum...
the problem with your boot lock is caused by
1-- the boot release handle lever stuck in
2-- the boot release handle micro switch full of water
the boot is lock is released by the release lever pushing on the micro switch which tells the BSI to unlock the boot catch.the micro switch is in the boot handle,this can be removed by removing the inner tailgate trim then removing the 2 securing nuts on the handle,disconnect the switch wire connector and remove the whole handle.
you can now check if the release lever is stuck,by moving the lever you should be able to hear or feel the micro switch click.
sometimes the little spring tag that returns the lever is broken or cracked causing the lever not to fully return ,causing the problems with the boot not locking,(WD 40 can be used on the lever pivot point to help free it up a bit )if you are happy with the lever operation a new micro switch is required these can be bought from any peugeot dealer
madmark
peugeot tech
Dave, December 2010