Ran across this great tribute site, for Roderick Timms, while doing a bit of surfing. It has tons of pics of the 71'6" BPB Mk V MGBs (the ones with the long, streamlined cockpit), after they were retrofitted WITH torpedoes, and renumbered and redesignated as MTBs. There were mentions of these in the books I've read, but most accounts were not quite clear on if/when they actually received torpedoes, near the end of the war.
This site, definitely confirms that, and provides lots of pics of the 35th Flotilla's boats, in action:
link
Make sure to click on the tabs in the left margin, since there are three sets of photos there.
From the accounts on the site, it appears the 35th Flotilla received their torpedo tubes sometime between March of 1944, and before D-Day. Exact dates aren't provided. They were also upgunned with a 6 Pdr. on the foredeck, which apparently was quite effective against S-Boats.
There are lots of pics of the BPB 71'6" Mk VI MTBs with the short, MTB style bridge/cockpits shown with torpedoes, but the long cockpit model (Mk V) photos with torps are a bit rare.
I'd post some of the pics here, but they just pop up when you click on them, so I can't get the direct links, unfortunately. Still, definitely worth a look, if you like British MGBs and MTBs.
Based upon the pics, if you want to do a little modeling of them, the following are shown with torpedoes on deck, in the photos:
MTBs 449 – 454 (just to be clear MTBs 447 – 454 are the Mk V BPB boats)
MTB 447 is shown in one image, but I don't see any torpedo tubes on deck (perhaps the photo is before her retrofit).
MTB 448 was not photographed, before she was sunk.
MTBs 478, 481, and 490 are all Mk VI models, with the shorter bridge cockpit (MTB style).
MTB 482, it is interesting to note, has a very large radar dustbin mounted on it, and is a MK VI model as well. Apparently, it was fitted with the Type 970 radar (fitted in Dec. 1944), that had a PPI display.