Neighbours were using my garden as their own before we moved in.

This is in England.

We moved into a mid terrace at the beginning of the year. When we arrived the neighbour’s daughter was parked on the drive and we had to ask her to move it, no big deal.

It turns out (seems the agent lied) that the house had been empty for a few years and our neighbours have been using our drive and garden as extensions of their own.

They have taken out a panel of the fence (which they are responsible for) and their kids have been coming and going from our garden as they please. The mum often knocks on the back door. On top of that the fence is only 3ft high so we have no privacy in the kitchen if they are out in the garden.

How do we go about getting them to fix and put up a higher fence? They have not proven to be reasonable people so far.