Garden measurement's do not match the reality by 15 sq m

Land registry in Ireland operate a non conclusive boundary system. It is specifically this way so that land registry won't get involved in identifying a boundary on the ground.

A surveyor is not going to identify a boundary down to 2 inches unless there are existing features on the ground.

I will say it again. Your overall plot size is the measurement to concern yourself with. If this adds up, all is good.

If there is a genuine encroachment at the neighbours boundary, it is worth looking at.

What does the planning say exactly?
Check your numbers, as the 106 crs 94.5 is not 15sqm.

What papers do you think they didn't check? You are purchasing the deeds not the planning permission.
Was a statement of compliance with planning provided?

The planning permission has nothing to do with what was sold. Certainly not to you. If the previous owner sole some of his garden, he is entitled to do that.

In that scenario, what the seller originally purchased isn't relevant. If you bought the car with 3 wheels and you had the opportunity to survey the number of wheels but didnt, the problem is yours alone as purchaser. There would be no come back in that scenario.

You still haven't said where the boundary is shown at the front of the property. Post a clip of the map from the land registry site.

It's all immaterial anyway. You bought what you saw. Where do you think somebody (who you think that somebody is, is another matter) will conjure up this 11.5 sq m from? Or, how much money would compensate you, even if you could find somebody responsible?

What scale is the map? 1:500? So 50mm at that scale will be 0.1mm. I don't think you can ascertain that level of detail on a folio map. You said there was a planning permission, what do those drawings show? The folio is what you bought, does that match what is on site?

Right, and in that case the car had 3 wheel when you agreed to buy it. You have no claim to the 4th wheel.

Surely you seen what was purchased when you bought it. Is the house you have now not what you see, and agreed a price for?
You were advised in this thread that you bought the land shown on the deeds, not the planning file. You solicitor has not said the same. Does that convince you that we were correct?

Does that match the boundary you have?