Any advice on getting our Water Meter switched on?!

Is the meter actually connected? If so, there may be a valve buried in the road outside. In our village, the Mairie had the key!

You need to phone or speak to someone face to face - only way to get things done in France ;-)

Write again but send by registered post and with an international acknowledgement of receipt required when they sign for it. A lot of French companies won't leap into action without receiving a lettre recommandé avec avis de reception. Advise them that you require a rendez-vous on site for the first week your partner will be in France.