Final Paperwork for Lease Extension

I have attempted to update my lease 6 times since the eighties and each time the freeholder have changed. In the last two years I have been pursuing the lease extension on my own with an unchanged freeholder. After another survey I filed Notice 42 and would like bids to send the final legal work for the extension. There are two small flats. I own the middle flat. The owners of the top floor flat live in Australia now, but I am in regular contact via email with them.
I am looking for a solicitor to dutifully assign the extended lease to us but they, (the freeholders), have not replied with the total number of years just yet. The Conveyancing Services Team Leader of the freeholders has just gone on maternity leave. I am in contact with her stand in.
The solicitor must be knowledgeable with English property law in particular an understanding of the finalisation of the extension. The lease is in my name. There may well be additional work available if I then decide to sell the property. The job is simple enough for the right person. I am currently in debt with two charges on my property. However I still have some savings left for this task.