my guess is that the detector head itself was removed and examined by the Danish navy. The second picture may be of more use, although small it was taken during the salvage operation, before the Danish navy got there hands on it.
I was in touch with the guys doing the salvage a few years back. As far as I know, the operation was a private venture, with danish and dutch EOD-personell handling the torpedoes and other armament/ammunition on board.
The submarine had 13 torpedoes onboard, including 5 G7s(TXI) "Zaunkönig II". They picked parts from 4 of those before they were scrapped, so the torpedo on display is the sole survivor.
Your photos is the same/identical as I posted above: If you look at my photo #4 and #5, they show the torpedo at it's current position before and after painting (there are also other photos showing the "refurbishing" being done in Birkenhead).
When a museum/collection choose to exibit a german WW2 torpedo outdoors they need to paint it, otherwise the corrosion will render it completly rusty after a few days, due to the low quality steel. Sadly, they often go for paint/color at hand, in stead of doing a little research, like for instanse the guys in Chicago did with their TV's (I haven't been there myself, but judging from available photos I think they have chosen a too dark grey colour for the warhead, compared to the seeker with original paint we have here in Norway).
Btw - here is a photo of the Kf warhead on display in Denmark (I don't know wether it's the same now on display in UK, but I assume so).