The unit code on ED559 was JA-D. I've seen that 100 Squadron at Waltham adopted HW. I've not been able to find out when the change was. I also saw on one site that JA was the unit code for 1652 HCU (Heavy Conversion Unit). So, to hopefully get some answers I posted a query on a forum.
UPDATE - I had a number of replies and added the detail about the JA code to the 100 Squadron page.
As and when information is found I'll post to this blog.
The last flight of Lancaster ED559