In a mosque in Cardiff's dockland, four British converts to the Moslem faith listen as the Imam of the mosque, Abdulla-El-Hakin, reads to them from the Koran - the Moslem Bible. Kneeling on the right is Ali Mohammad, one of the Mosque dignitaries. Scenes like this are not unusual in Cardiff. The Arabs in Tiger Bay - the dockland area - number 3,000, forming the largest Moslem community in Britain. Many of them marry Christian girls, and in most cases when that happens the girls adopt the faith o