Will Land registry backlog affect my mortgage application

Shivarety

Context: I own a share on a shared ownership property. I'm trying to staircase (to own 100% of the property) which will involve further borrowing from the bank. I recently extended the lease as it was approaching the 80 years dreaded limit. Land Registry has suggested that completion of registration of the lease extension is estimated to be on 14/05/2026.

The solicitor has advised that I expedite the registration to facilitate the purchase. For this they recommended I provide the mortgage offer to send to Land Registry to prove that I need the application to be expedited. It's taking me a bit longer than expected to get the mortgage offer as the bank is asking for further documents (long story short, it's all to do with aversion to risk taking since Grenfell). I'll definitely get a mortgage offer, either with my current bank or remortgaging if necessary, so that's not my main concern. But I do want to complete the transaction before April 1st when Stamp Duty legislation changes, so the Land Registry estimation of 2026 isn't ideal.

I'm a bit worried that the delay caused by the bank will mean that I won't get the Land Registry application sorted in time, so my question is: if I don't manage to expedite the application in time, will this impact my transaction? The last official copy of register of title already shows the property under my name, it just doesn't show that the lease has been extended, so I'm not sure how critical it is that I get this application expedited in time. If the current title as it is won't be a problem then I'll sleep much better!

Any ideas?