Originally Posted by travelmad478
my choice: go through immigration, park your bags at Left Luggage (£5 per bag, in the arrivals hall) and have a day in London via Heathrow Express
If you choose to do this, there's no necessity to collect your bags. Just make sure they're through-tagged to JNB and they should be transferred automatically. Then you can go through immigration and waltz straight out through Customs and get going into London. (And you don't have to pay the Excess Baggage Company.)