If you only need to lay one bet at a price below 2.0 and have it matched, then that's different. In that case, I can suggest monitoring the prices with a trigger and laying on the first horse whose price is less than 2.0 (say, 1.85 or 1.14), but offer a price of 1.95 (or any price limit you will key in). The idea is to let BetFair adjust your price automatically. If the horse's current price is, say, 1.50, then your offer of 1.95 will be automatically adjusted to 1.5. If it suddenly leaps to over 2.0, then it will stay unmatched. In any case, such bet would increase your chances of it getting matched at whatever price you can afford (below 2.0). If the bet is matched, the trigger will not place the second, third etc. bets on other horses. If it is unmatched, it'll be cancelled before a second bet is placed.
What do you think of this? I can make you such a trigger.