Britain's Ministry of Justice produced these figures listing the prison population of England and Wales by religion. The figures go up to 2008 but I'm going to take a snapshot of prison population in March 2001 since the last British census was held that year so we can see which religious groups are disproportionately represented.
Prisoner populations of each religion, as a percentage of total prison population
All Christian - 59.16% (Anglican - 37.8%, Catholic - 17.47%)
No religion - 30.92%
Muslim - 7.47%
Buddhist - 0.69%
Sikh - 0.63%
Hindu - 0.41%
Jewish - 0.25%
Here is the Office for National Statistics Census Results for 2001, dealing with the sizes of various populations. With a full population for England and Wales of 52,041,916 in 2001, we get the following results:
Percentage of population in England and Wales of each religion
Christian - 71.7%
Buddhist - 0.277%
Hindu - 1.06%
Jewish - 0.5%
Muslim - 2.97%
Sikh - 0.63%
No religion - 14.8%
Unfortunately the Census did not break down Christians into various denominations, though I suspect Catholics must be overrepresented among prisoners.
Underrepresented religions among prisoners
Overrepresented religions among prisoners
We need more data really, to make sense of this. For example, some of these religious groups are probably associated with fairly recent immigrant groups, who perhaps have a younger population, or a greater proportion of males, than others. We also don't know how strong the religiosity is of each group.
Still, it is interesting. Why are Muslims, Buddhists and nonreligious people disproportionately likely to be in prison?