Messy lease and wrong title plan

[Yorke8548]

hi all,
We are trying to purchase a maisonette first floor. Both flats were under the same lease registered in the 70s with this lease referring to a lease from the 30s which also covered both flats, then in the 80s the ground floor flat was given a separate lease and the FF flat is now the only property remaining under this lease (70s). The ground FF title plan shows the boundaries of their flat and garden only, while the title plan for the FF flat shows the whole building as well as the lease plan shows the whole building.
My solicitor has asked for the plan to be corrected but the seller's solicitor does not seem to think it's necessary as they are saying that the plan clearly shows the inclusion of the flat. There is not dotted line dividing the 2 properties, the whole building edged in red.
Has anyone been in a similar situation?
Would deed of variation sort the issue.
Any advice thought would be most appreciated.

What would the deed of variation do? Why would that be less trouble than having a new plan drawn? What does the freeholder say?

When I moved into this place, my solicitor asked for a new more detailed plan to be drawn. It was an extra expense for the sellers, but nobody made a fuss about it.

I would listen to your solicitor. He or she is looking after your interests.

It's a share of freehold. The seller's solicitor drafted a deed, no indication what part of the premises belongs to the flat we are purchasing. They have not provided copy of the lease plan to my solicitor.
My solicitor suggested entering into brand new lease to include correct plans etc. and remove all references to old leases but the seller's solicitor is reluctant and drafted a deed instead.

My solicitor has made further enquiries, so we'll see what they come back with.
Yes, we'll go with our solicitor's advice.