Andrew Ritchie, the inventor of the Brompton Bicycle, gave a very entertaining, but also extremely informative account of what it takes to invent and market a new consumer product in the hostile world of British investment finance.   He devised the first bicycle in the bedroom of his flat opposite the Brompton Oratory and then spent several frustrating years trying to raise capital from long-suffering friends and avoiding being taken over by bigger operators, including Raleigh.   It was a classic story of Samuel Smiles perseverance in the teeth of suppliers of components going bankrupt.   Now, after twenty years of success and after moving into a new factory, the Brompton has become too expensive.