Most of the people working at Heathrow are Sikhs lol. The surrounding areas southall, hayes, hounslow all contain the largest sikh populations in Britain. Maidenhead also has a large sikh population, with it own gurudwara. You wont have any problems at Heathrow, unless of course they have good reason to question you. Brits have a good knowledge of sikhs, and are generally warm and welcoming.
Guru Nanak Sat Sang Sabha, 31 Rutland Road, Maidenhead, SL6 4HT. Although most programes occur on weekends.
Slough is very close to Maidenhead, and has a gurudwara as well.
LSE, stands for the London School of Economics, its a university. If you need infor about getting there etc.. please dont hesitate asking.