The Wikipedia article you linked to is NOT the same Benjamin Anderson who worked on the Kill la Kill soundtrack. They were born in different countries, in different years, and have absolutely nothing else in common.
The correct Benjamin Anderson was born in London, UK and currently resides in Japan.
As it mentions on his profile, he is the singer and songwriter for CODE.
December 11, 2013 entry:
Recently Easy T (Jun Tatami) and I (Benjamin Anderson under the moniker 'mpi' have been writing lyrics and providing vocals for tracks on the Kill La Kill original soundtrack CD being released on christmas day this year! The tracks are 'Suck your blood' and 'I want to know'. Check them out on release! 最近僕 (Benjamin Anderson)とEasy T (Jun Tatatmi)はキルラキルのアニメのサウンドトラックCDの為にボーカルと歌詞を作ってあげた。 Suck your bloodとI want to knowは ２５日１２月２０１３年 リリース！ 我々の仮名はmpiです！ 皆さんチェックして楽しんで下さい！ 宜しくお願いします！
Keep in mind that they did not contribute any music, only lyrics and vocals.
You also asked about other vocal work he's done, so here are pages for his main band, CODE:
And here are his personal pages at other sites, using various aliases:
He also did keyboards for a group called "Split Works" in 2006:
http://www.discogs.com/Split-Works-Wide-Open/release/4735590
Additionally, you can find all the comments he's made on YouTube videos here:
https://plus.google.com/104914344750776651199/posts
In Kill la Kill, he was the singer for "I want to know", and he provided vocals for "Suck your blood" along with Jun Tatami. The comments shown in the above link make it clear which vocals are his: the segment of "Suck your blood" which played during episode 10 was entirely sung by Jun Tatami (http://youtu.be/qOMdlzwn4V0?t=15s).
On a side note, I should point out that "Jun Tatami" (the bassist and backup vocalist for CODE) is not the name listed on the credits as the second vocalist for "Suck your blood". Instead, the infamously anonymous vocalist "mpi" was listed.
Taking that into consideration, and comparing Jun Tatami's voice to mpi's, it's clear that they're the same person.
This is the vocalist for "Call your name" and "The Reluctant Heroes" from Attack on Titan, and "friends" and "Hill Of Sorrow" from Guilty Crown.
I hope that's enough information for you to be able to keep enjoying the vocals of Benjamin Anderson. His YouTube channel in particular seems to have quite a lot of music on it.
