Not proclaiming to be an expert in the field or of the Anson BUT...
It was not the first Low wing mono and first with retractable UC in the RAF. It was the RAAF. Might just be a typo on your part, but I thought I would just point it out.
Also, the sub that it bombed, You sure that was not the Snapper. I seam to recall reading that it got a few light bulbs broken when it got accidently bombed by an Anson from coastal command.
Shortly after that incident it was re-assigned as a trainer.
Ian M