The ones that survive will be back to recruit even more jihadis. The UK's human rights legislation has made anti-terror legislation close to useless. The high court regularly overturns any such laws as violations of human rights.
Last week the court ruled that all prisoners have the right to vote. A few years back, they ruled that non-citizens have the same -- or more -- rights as citizens, seriously impeding the ability of the government to hold suspected foreign terrorists for more than a few days without specific charges.
Zarqawu and his ilk know a safe haven when they see it.
It is the EU Human Rights Charter that causes the problem and not UK legislation but this is being examined at the moment in light of 7/7.
As for prisoners voting that has little to do with terrorists, but I see nothing wrong with a citizen of a country voting. Democratically that is their right.
The UK has recently banned a whole plethora of groups from the country because of their terrorist links.