I had a good look at both the GRO post 2007 death indexfiche at the British Library today and searched the indexes online.
The GRO results online do not show the full date of birth, only a year.
The GRO results online do not show the specific month the death was registered, only the corresponding quarter.
Interestingly, once you have identified the death entry for your person of interest, you can click on the radio button to the left of the details which then takes you straight through to ordering, so you don't have to fiddle around entering the registration spellings (right or wrong), entry numbers and dates of registration.
However, the death indexes on fiche at the 7 host sites do contain the date of birth as provided by the informant and the actual month of registration.
So if you are happy just with the index details rather than the specifics then this is a way of killing of those distant twigs on your trees until you get a chance to go the the 7 host sites for more of the registartion details.