Thanks for more fascinating comments. I have done a little.
Removed dust, tested the fan with a 9v battery which gave a gentle flow of air out, installed the Custom Firmware. Twice, I should have copied the instructions, forgot to remove the memory stick. I did remember to empty the stick but forgot to format it. It all worked smoothly anyway. The recorder has survived and recorded Fireman Sam this morning ok. Ordered an Ethernet cable. I may be able to borrow a Windows 7 laptop that has been unused for several years.
I have ordered a wifi dongle on eBay but I confess that this aspect of this project is the bit that really bothers me. I will not be at all surprised to find that it does not work with the recorder.
I could not find on the Vodafone/Huawei account site the AP Isolation topic. But since it is mostly meaningless to me that doesn’t mean a lot. I suppose it might be possible to take screen shots of the site if that would be of any interest to you. I suppose I would attach them by the ‘attach files’ near this posting form.