can a neighbour put posts in my garden without permission

If its their fence they can but its normally polite to tell you first, and you've also got a new fence for nothing

They certainly cannot - that’s trespassing. You have a right if access to a neighbour’s land for essential maintenance under the Neighbouring Land Act but not to leave anything on it. If you trip over whatever they have put there, you would be able to make a claim.

Who evers fence it may belong to the new fence has to be place along the same existing border line. In some cases people are still Un sure of this and can sometimes be found on the deed to the property. And ever when doing so I would still always knock the neighbour's door to be polite and make them aware of the works taking place and exactly what works I going to be carrying out, also telling them I may have to come onto there property at some points while carry these works of erecting the fence as this some times can prove to be impossible without going onto the neighbour's Land. Hope this answer of my professional knowledge helps. Kind regards Jay. The Fencing group ltd

It would have been nice if they’d asked before they’d started work but if they’ve moved the fence more into your garden then that’s not on because that’s your property

They can if it is there fence but it's always nice to consider your neighbours and ask you first, they cannot of its your fence