If the boundaries are defined by block walls then these are the boundaries, the land registry register property not boundaries and therefore make no comment on exactly where a boundary is. The land registry when moving fully digital recreated all the old 6inch to 1 mile and 2500 drawings to the new osi maps. In many cases if the old and new maps were close enough the folks in india simply snapped the digitisiesd land registry boundary to the new osi digital maps. Now any line on the osi map represents a feature on the ground but aggregation can occur, e.g if a block wall and a fence and hedge are all within a 500mm band then only one line is shown and no reference is made as to what that line represents. Then you have the scale at which the map is printed, typically in dublin the published scale is 1:1000, typically at 1:1000 the accuracy is about +/- 300mm. In urban, suburban and periurban mapping, the results of testing 36,929 points of hard detail are that 93.2% of the points in the mapping are within 1 metre of their true ground position, and 99.1% of points are within 2 metres of their true ground position.
If you have a solicitor insisting that a survey is carried out, I think they generally mean they require someone to look at the property to make sure for example an extension is not built on someone else land etc. i.e. a mini declaration of identity.
If you employ a surveyor to map the boundaries to millimeter accuracy, it is a fact that they will not exactly line up with the land registry boundaries, so in that case what does the solicitor, the surveyor, the vendor and the purchaser do in that situation. either stall the sale (indefinitely) or revert to the non conclusive boundary system successfully employed by the landregistryireland since 1964.
If the land registry maps appear correct in shape and proportion and if everybody agrees that the block walls are the boundary then you don't need a survey, if the land and building are contained within those wall then you don't need a survey to tell you that.