When to split 2 Garages onto separate deeds when selling.

Hello,
I have 2 garages in a block of garages, not attached to a house.
They are freehold and on the same deed number.
I have 2 buyers who each want to purchase a single garage.
I will be doing the conveyancing myself.
At what point do I send in form AP1 to separate the garages into two separate deeds?
Doing it at the end of the conveyancing process after exchange and completion doesn't seem quite right.
Thank you.

Hello Andrew - you don;t have to split to sell as you would sell one as a Transfer of Part (TP1) and then the other as a Transfer of whole (TR1) for example. It's then for the buyer's to register their purchases and not you
How to transfer ownership
Splitting a title 

Thank you, Adam.   So do I send the TP1 to one of the solicitors, and the TR1 to the other? And I presume it is my responsibility to pay your fee, so do I just send it to one of the solicitors to forward to you when they register their client's interest, and then the garages deed is finally split into two?  And since you will be receiving the TP1 and TR1 at different times probably, will that be a problem, especially bearing in mind the first to arrive may not be the one with your fee cheque enclosed ?  Many thanks for your help.

Andrew - yes if that's how you/they ant to deal with it. 
Fee paid on application so that would generally be the buyer
In light of your Qs and uncertainty I wold recommend seeking legal advice/assistance or speak to your buyers to confirm if they are using conveyancers and if so deal with what they ask for rather than your own assumptions
I mean that in the nicest possible way and not as a criticism of your Qs as the guidance on how to complete such Transfers is set out online but we can't offer the wider guidance you appear to require here. These things can appear simple on paper but there is a lot to consider before you get to the point of actually applying to change/update the registered information 
I would suggest reading through the forms and guidance re how to transfer ownership to identify what's required from You. Then speak to your buyers with regards what's required from Them. And if that leads to Qs re the conveyancing and who does what then seek wider advice and answers as required.