Boundary on land registry plan incorrect

Me and my partner are in the process of buying a house and we received the land registry title plan. The plan outlines the boundary however the boundary is not inclusive of the front garden. The front garden is attached to the house by a wall and is quite clear looking at the property that it belongs to the house - however this is not reflected on the title plan.

The front garden in question I believe from searching land registry records is not registered separately or under another name so it is essentially ‘no man’s land’.

The sellers and their solicitors have been quite unhelpful on this matter so far and have just stated it’s always been like that since it was built by their parents and it clearly belongs to the house. We don’t dispute it belongs to the house but obviously we have an issue as it’s not reflected on the title plan.

We wondered if we got an affidavit from the seller (child of the deceased’s estate) stating that their parents had use of the land since it was build - would we then be able to apply for the land ourselves after the sale? As it’s looking difficult to get the sellers to action anything directly with land registry.

Any other advice would be appreciated. I have attached the plan in question - that shaded blue is the front garden.

Katie - if the title plan/registered information does not match what's being sold than a claim as to adverse possession of the land can indeed be made
IN my experience your conveyancer asks you to check and if no match they then go back to the seller's conveyancer to raise the issue.
The choice is then whether they apply to register the land themselves first or you buy having relied on their statement of truth for example re the claim mentioned
Being 'unhelpful' isn't really an option usually as you, your conveyancer and any lender are very unlikely to complete without resolving the issue as raised. And if you are buying with a mortgage then your lender is really going to have the final say also

Hi Adam,

The problem is we don’t want to loose the house over the boundary being incorrect. Obviously we and our solicitors are pushing the issue as much as possible. 

If we got a affidavit from them stating the land has been used by that property since it was build (1994) would that be enough for us to apply for adverse possession? As obviously we personally wouldn’t have had use of the land for 12 years but the property itself has?

Hi Katie - that's what you would need from the seller as per the linked guidance from my earlier post
Your conveyancer should be aware of what's needed to enable you to exchange/complete and then seek to register the additional land. 
So you/your conveyancer need to ensure that the affidavit includes all the required information/facts to satisfy the legal requirements. If it does then you can apply to register that claim or they can do so before you complete on your purchase