Next round, because I will obviously win ;) I will bet my £50K, plus winnings on a single bet in round 2?
Yes, all as a combined, single bet. You can't bet on the other side personally, i.e. offsetting your bets to win win when placing it. It is a single combined bet of your amount + winnings until you either lose it, or you walk away with a million + at finals if you make that much.
To give you an idea. Nicolette bet her $50k on Silvia Soler-Espinosa at $2.00. She got back her $50k (initial bet) + won $50k (difference 2/1 odds). She has a total of $100,000 to now bet next. Because that game finished, and Svetlana Kuznetsova hadn't started yet, she bet that $100,000 on Svetlana Kuznetsova at $1.13. She won, she got back her $100k (initial bet) and won $13k (difference in odds, being 13 cents) for a total of $113,000.
Still in round 1 here. She has now bet it on Olga Puchkova game which starts soon, the entire $113,000 as a single bet, because it is the total she has reach thus far and it must all remain together. Olga Puchkova is $1.53 if she wins. If that occurs, then Nicolette will have $172, 890 for her next bet, which she must keep together. That is her original $113,000 bet + the difference in winnings of 53 cents on the dollar, which would make $59,890.
If she wins that game today, she will still be in round 1 tomorrow with more games available for her to increase her earnings.
As you can see, it hasn't increased all that much after two wins... the third will make it healthy IF she wins that one. Otherwise, she loses it all on the bet. If she makes it to tomorrow she can then strategise to bet on several games again based on their starting times, hoping to build the amount so she can then take safer bets on favourites in the coming rounds who will not have great odds typically, thus the money is less, thus the chances of reaching $1m is more difficult.
This is why you have to really take big risks or lots of little risks by a multiple betting strategy in each round. That is hoping it works, because some games go over, they move games to different courts, all sorts of things change in tennis.