For those of you who noticed that I posted a reply which has now disappeared, this is because I was prompted by roll17's questions to me to go and check my facts again - so thank you roll17
This is how the process works in Lincolnshire, but it is worth noting that although there is a national set date for initial allocations of 1 March, what happens after then varies considerably from authority to authority:
Initial allocations for on-time applications are notified on 1 March.
Late applications have an allocation date some weeks later - this year it was 25 March.
In the intervening period no allocations take place. So no-one on the reserve list from 1 March can be offered a place, even if some people have rejected places, until the second set of allocations take place with all the late applications added in to their "correct" position on the reserve list.
The third allocation is for revised applications or other applications which arrived too late to be considered alongside the late applicants. This was today, 29 April in Lincolnshire. Again no places will have been offered in between the late allocation date and the revised allocation date.
Once this final block allocation process is done and dusted the system switches onto rolling allocation where places are offered as and when they become available to the next person on the reserve list.