Buddhist temples in London and donations?

I am highly intrigued by Buddhism and would like to follow it. I would like to visit a Buddhist temple in London to speak to a venerable or a monk or a teacher to help me with it and show me a place to start. However, I was most disappointed to see that all temples and meditation centres ask for donations in return. I haven't got a problem paying but have read that places that ask for money are cults. How do I differentiate whether or not the temple/ monastery I visit is indeed aimed at spreading peace and not fleecing people out of their money. Also, does anyone know which would be a better place to start, a meditation centre or a temple? Thanks.