The next day I decided to measure the output voltages from the adapter which had gone wrong, but it had recovered and worked perfectly again, weird, I didn't know such things had bad days.

Eventually the adapters arrived, all were encapsulated in the same ultramarine translucent plastic and all appeared in 'Device Manage' as CH340, that is after I had managed to find a driver. After I had found a driver two of the adapters came with mini CDs.
They must all have the same identification string because you can only have one plugged in at a time.

All of them only output 0 and 4.1 volts rather than true RS232 voltages. DTR is active but I haven't tried the other control lines.

The strange thing is that even though all of them will enable me to talk to the robots from a terminal program (my choice is Br@y's Terminal) only two, from the same shop, will allow the PicAxe editor to see and program PicAxe chips, no control lines are involved as the PicAxe editor only uses Rx and Tx at 0 - 5v to program PicAxe chips.

I don't have a storage scope to capture the programming protocol to see what is missing.

Will program PicAxe
- megoshop2012 eBay
Won't program PicAxe
- Cell Phone Cases (with CD)
- chips-fans eBay - with attached lead
- der_beste eBay - with attached lead

However apart from Cell Phone Cases they all seemed to be drop shipped and the details on the envelope bear no relation to the eBay seller.

So if you buy adapters from China your mileage may vary as they say.