Extending garden wall onto garage driveway.

The laws on this can be ambiguous. Firstly if the land belongs to you then generally yes you can build a garden wall without planning permission. The details of the land owner will be located on your property deeds and land registry. The deeds should also tell you who is responsible for maintaining the boundary. It wont get your neighbour to pay for it but if it is your responsibility, it would be a helpful piece of information to have in case anyone complains about your new garden wall. I do not think you need planning permission for a garden wall and the council wont tell you what permission you need, if any. This would be your responsibility to determine your boundary and whether you need to apply for permission. Check the permitted development guidance to see if it applies to you if it is some sort of extravagent castle like wall but if we are talking something knee height I personally cannot see it being an issue for you. If you are on a boundary at all then you should agree something with the other land owner and I suggest making an agreement with the party wall act if your neighbour is a difficult person so it covers your back. Also consider any shared access for your neighbours. I havent seen the site but if you say the driveway backs on to your neighbours drive, will your wall affect the neighbours access? In your situation, I wouldnt over complicate any more than needed. If the PD guidance does not apply to you, I would speak to the neighbours who it may affect (if it affects them) and inform them of what you are going to do. If they have any issues then be reasonable and try to address them if these issues are reasonable of course (some people are just difficult). It will save you a potential headache if they complain to the council after the wall is build and say it is restricting their access! If everyone is happy I would say go ahead and do it.