Just forget any GA during the Olympics in London area. You will not be welcome!
Not just in the air. Traffic on the ground will be a nightmare, with ZIL lanes for Olympic traffic reducing road capacity, and public transport similarly constrained. Some hotels have been speculating that Olympic business might not make up for loss of normal business revenue, as everyone not involved in the Olympics is treating London as a Total Exclusion Zone for the summer.
We often have business meetings in London as it's often the easiest place for everyone all around the UK to get to, but over the summer we'll have meetings on Pluto in preference to travel to London.