I don't have any business meetings in London MANFOD, but our company has a subsidiary in the south west corner of Hampshire that I visit regularly. The obvious choice for a visit is a direct flight OSL-LHR, but I have had a number of other combinations like OSL-EDI-SOU, OSL-MAN-SOU, OSL-DUS-SOU and OSL-AMS-SOU. From arriving LHR to being parked up outside our facility it takes 3 hours if the M25 is in happy mood (the 4.2 miles can take hours if you have a gas leak in the neighbourhood) and if I allow my self a stop at either Fleet or Winchester Services along M3 for an espresso and a toilet visit. Public transport is really not an option to our Hampshire office as for many other locations in the UK.
At the other end it takes usually 55 minutes for me to get from our office situated at the west end of Oslo to the Non-Schengen gate for the flight to LHR, and that includes time to check in baggage, time to pick up some small presents from the duty free shop for the ladies and 32 minutes on the Airport Express Train. OSL is a building site these days (and will stay so until early 2017), but still the waiting time at the security check is only 4 minutes according the airport website.
For direct flights from OSL to MAN you can't pick and choose - either you are lucky and avoid the ME3s or you hit them big time (late SK4609 and early EK17 is the perfect combination).