Update as promised.
So just came back from ChangW immigration. NON-B visa extension date cancelled/changed to 8th April, last day of work. No problems. Then COVID extension until 2nd May (under consideration stamp) when I have to return to immigration. No problems. I assume this is standard and then they will stamp for another 30 days? Is this right? 5 Hours in total but worth the wait. Once again thanks very, very much for all your help and advice.