Have you managed to fix the annoying electronic noise problems?

Yes I believe so - that is why I had more PCBs made But I also took the opportunity to add 512k RAM expansion and a Compact Flash card interface as it became clear (thanks zozo!) that Compact Flash cards support 8-bit mode and it would not take any extra hardware except the socket.

With hindsight I wish I had used the ESP8266 from the start, but back then there was very little documentation, and only in Chinese!

Still there is a possibility to use a ESP8266 module connected to your WIZ card, by means of some sort of RJ45 to RS232 TTL adapter.

Thanks, but if we're using adapters something like this RJ45 to wireless adapter should allow wifi much easier than  getting involved with the ESP8266, but I haven't tried it (yet!).