Spent mine in IDA leceister (Shaykh Saleem Dhorat). It was beneficial as always. To be in his company and hearing his advices/words are priceless, also the environment of actions (nafl salat, dua, quran, zikr etc) is like a magnet, and a person who comes there will find it so easy doing these amaals. I took 2 brothers with me last year to IDA, this year 10 came, and now the brothers have inserted itekaf as a fixed schedule every year inshallah. First 10 days or the first 20 days we go in Jaamat, and the last 10 days in itekaf.
Hazrat Mawlana Ayyub Surti Sahib (Majlis e Dawatul Haqq, Leicester UK) was in Zambia this year for I'tikaf. He recalls the I'tikaf in the following audio 20th August 2012 Islahi Majlis - Safarnama which can be found here http://www.majlisedawatulhaq.org.uk/index.php/audio Briefly, he says that when he was younger, he experienced I'tikaf with Hazrat Shaykhul Hadith Mawlana Zakariyya (rahimahullah) and that the I'tikaf in Zambia reminded him of those days.