Well I'm not sure tbh. The raw numbers are fairly small.
And you need statistics to find the number of black transgender. Transing is frequently a response to homophobia (see Iran, Indonesia, etc.). Lots of black communities are VERY homophobic.
According to stats the US trans community breaks down as 55% white, 16% black, 21% Latino, 8% other (vs. 65%, 12%, 15%, 8% for the wider population).
Anyway generally around half of murder victims are black. ucr.fbi.gov/crime-in-the-u.s/2011/crime-in-the-u.s.-2011/tables/expanded-homicide-data-table-2
So around 4 times the underlying population. So we'd expect 64% of transgender murder victims to be black. Looking at the pictures here: broadly.vice.com/en_us/article/hes-not-done-killing-her-why-so-many-trans-women-were-murdered-in-2015 it seems the rate is even higher than that.
But I'm pretty sure that's not about Jenni Murray or Trump bathroom laws, but if it's anything, homophobia among black people. Although you can't say that for sure without adjusting further, there are many obvious factors that may result in no net difference
"The majority (13) of the 23 trans women killed in 2015 were under 25 years old. "
"Black trans women were 44 percent more likely to engage in sex work than their white counterparts. Latina trans women were 33 percent more likely"
Young black men are something like 100x more likely to be murdered than say, old white women. So if disproportionate number of transwomen are young, then the murder rates will be higher.
Either way I would say
(a) this has nothing to do with Britain
(b) transwomen as a whole are not at special risk
(c) if there is an at risk group it is specifically young black transwomen, but then young black men are also at risk.