Well, I lived in the UK (different parts and including London) for some 7 years. Next to Indian and Pakistani population, Arabs were the largest community especially in London. That was in the 80s unless they've moved?
Nope. Number of Arabs is tiny in the UK. Figures from the 2001 census are available at http://www.statistics.gov.uk/cci/nugget.asp?id=273
UK population (in 2001 census) is 92.1% White, 1.8% Indian, 1.3% Pakistani, 0.5% Bangladeshi, 0.4% Chinese, 0.4% Other Asian, 1.0% Black (Carribean), 0.8% Black (African); Arabs are too few to even register as a category