Not sure about that Val. One of her concerns is that agencies have different commission rates, negotiation is always possible and there is a lot of promising and breaking promises going on. However, people coming to France with hard bitten ideas about negotiating, as is done in other countries, run a serious risk of finding their dream house then putting the vendors off by making offers that are far too low. Sometimes agents do advise against accepting offers but often it is people selling property themselves who will not budge. So when clients get angry with agents about negotiations not going as they wish, then they are often losing a 'friend' in that to compensate when a deal simply does not work, the agent will put themself out to find a property that matches expectations.
Notaires are another story. They are both business people and public servants. About 60% of their commission goes to the government as tax and stamp duty. They do not get €10,000 from a €10,000 commission. They get about €4,000. So they too are out to see the highest possible prices. The service they offer is very variable but they should be treated with delicacy. A while ago somebody aggressively emailed notaire and both parties involved in a sale of land. He told the notaire exactly when he would be there, ditto the two buyers and demanded that an English speaker be there for him. He gave a day and exact time. He chose a Friday at 1330. Firstly, lunchtime so there he was already on a hiding to nothing. Then he did not account for the fact that either buyer may not be available. One was certainly not because he was away on holiday in Spain. The other just felt put out at being told what to do so just did not reply or make any attempt to see if there was any alternative. So the vendor arrived on flight X, collected a hire car and drove to where his appointment had been set by him. The notaire's office was closed, nobody was there. He waited, around 1400 somebody showed up to open the office. He went in and hit a brick wall of no English (the secretary probably can but...) until a junior notaire showed him up and said Maître X would not be back that afternoon because she had appointments elsewhere. The man demanded this assistant do the work, but she refused saying it was one of her boss's own assignments so she was not entitled. The man made a terrible fuss, tried shouting about how important he is and basically achieved nothing. Except that is, that he found himself with completion of the sale of his land almost four months later than he had originally expected. The notaire did everything at her pace at effectively punished him.
The point in telling that tale is that they have the upper hand, it is probably best to go along with their pace and way of doing things as much as it displeases you. As Sean says above, they are quite capable of playing silly buggers with money so make sure you remain on totally friendly terms with them and agree the best you can get out of them.
As for the rest Roland, if you have ever played poker then you will understand the need to be emotionless, straight faced (even when winning a lot), patient, never letting anything out of sight or pass by unnoticed and then you you are probably fine. If you have a good agent who can work well with notaires then you may have somebody doing the playing for you and letting you tag along for signatures and other formalities. Standing screaming on their doorsteps does not work.