FWIW I believe the Excel London centre is outside the congestion zone, so if driving it's around the M25 and drop down to docklands. I may be wrong though. For me, NEC was fairly easy (1 hour drive plus advance-booked parking), After moving house next week though, it'll be either fly or ferry+ drive, which means obviously flying in reality, which limits what I can buy, but on the other hand there's precious difference between BHX and LCY flights. I'll probably give it a go at Excel, as I missed it this year.