Thank you for your post regarding your later father Jack Sidebottom. I don't have precise details of the incident for which your father was awarded the DSM but the London Gazette
entry for his citation may be found within the issue for 10th October 1944. The link provided will take you to the citation, and the next page lists his name.
We have an extract from the biography of Ken Forrester
available on our site, who served onboard MTB 632, and which you may wish to read, as it will provide you with more insight into the workings of that boat and the flotilla of which it was a part.