Following the advice of those without a clue is probably the best way to find a solicitor's letter dropping onto your doormat.
Rights of way (easements) come associated with a parcel of land - not with any house that might be located on the land, nor aligned to one particular owner of the land (easements are often written as a right to 'successors in title'). The current owner of the parcel of land at the end of your garden that has the benefit of the easement over your land can therefore very likely sell part of that land and provide the benefit of the easement with that land transfer - whilst still retaining the easement through his ownership of part of the original parcel of land (on which the house sits).
So, whilst one cannot be sure (because it depends how the wording of the easement was written into your and his land title register), there is every possibility that what he has done is legally possible and there is no requirement for you to be consulted. It doesn't matter if he can no longer use the original access to get to his garden - he still has the right to walk up there.
HOWEVER, you raise a tantalising issue: an easement is normally written to show a described route on the title deed plan to get from one side of your land to the other - not wander around aimlessly inside your confines of your whole plot. So if you are saying that he thinks he has the right to wander off the route all the way along the far boundary that adjoins the side of his house, he is very likely to be wrong. Ditto the new owner who thinks he can wander along the other side of the far to cut his hedge. Normal neighbourly courtsey often means that such access is agreed once a year for this to be done, but as a legal right, that sounds a bit far-fetched.