The wifi fix didn’t last long as a solution. On the next heavy rainfall the central locking system wouldn’t unlock the doors when using the remote fob. Luckily it appears to now be fixed, well it’s been working fine for the past 5 months.
Given that it appeared to be a signal degradation problem I open the fob and used electrical tape to strap the 2 batteries together and to the contact. This appears to have cured the problem. My reasoning is based on the supposition that only a single battery of the two was being used and consequently more susceptible to interference. Strapping them ensures more signal strength from the fob and less signal inference from wifi or environment issues such as rain.