London based executives tend to maintain a reasonable level of formality in their business relations, at least at the initial stages. They are unlikely to address you by your first name until they are invited to do so.
Punctuality is important. If you are going to be late for an appointment, telephone and let them know what time you expect to arrive.
The exchange of business cards is often done towards the end of meetings, however be prepared to exchange business cards near the outset of the meeting.
Most London Executives expect to shake hands with business associates.