Temporary title number not being accepted by solicitors

We have purchased a new build on the new Ashmere development at Ebbsfleet in Kent. Our solicitors are now saying they cannot proceed until the full land registry document is completed? The developers are telling us to change solicitors to one who will accept the temporary title number however they say it has been expedited and is now in a queue? Is it possible for someone to please tell me how long it will be before the full document is completed? 

Faye - we can't be definitive re timescales as it reads as if the expedited application is behind others with 'priority' and submitted against the same seller/developer's title. Hence the hold up
I should stress it's likely to be less about the 'temporary title number' and more about the fact that your mortgage lender won't proceed until they have a new and registered title.