"I can also delete a title from a group of recordings. However, bear in mind that the space the original data occupied is not retrievable until a full erase is carried out".
Just for the record - some recorders can use this space. If I record say 6 one hour progs on a 6 hour DVD I can delete any number and record over the gap. I can also delete any part of the program and use the space to re-record over.