As Reinaart says, Mediterranean MTBs at War by Leonard Reynolds and H Cooper is the best place to start. There's quite a lot on her in there, including descriptions of individual engagements she was involved in. In summary she served in the 24th MTB Flotilla, initially in Home Waters and then in the Med, under the command of Lt Strong. She appears to have been heavily engaged during the Sicilian campaign and was present at the notorious Bari raid in December 1943. Strong appears to have been promoted to the 10th Flotilla in 1944 and 81 had a few different skippers. In July she accidentally struck a damaged boat, causing damage to her bows. Apparently she was already expected to be paid off, so this may have marked the end of her active career.
A few of these plaques have cropped up in recent years. You might find this post on sister boat MTB 83 of interest:
Likewise I've posted some information on sister boat MTB 85, which served in the same flotilla as 81, on my Twitter thread:
https://twitter.com/SeaSpitfires/status ... 1826343942
And scattered all over this thread is information about MTB 227, including her plaque (although she didn't serve in the Med). You need to click on some of the posts to open the multiple replies:
https://twitter.com/agbdrilling/status/ ... 2582204417