Think you might find that dlf 3 is actually a soft kill decoy for asm, it's inflatable and has a very large RCS, nothing to do with ASW. The 23 have their torpedo tube fixed at the forward end of the hanger structure in fixed athwart ships tubes.Sounds like the DLF-3B decoy system, that's what the Type 23 has exposed as the torpedo tubes are built into the structure. You've gotta look real hard for the circular hatch which pops open and the torpedo launches out.
They're ASW decoys, you see 'em around the VLS on more modern Type 26 models.
I'm glad some progress is being made on Harpoon, initial reports were that they'd be fitted by the end of last year. Still, hopefully the modification is made to all ships and they move the 4 sets of Harpoon around.
Happy to be proved wrong though.