Betting a lot somehow acts as an invisible handicap on the horse. This leads to several observations:
1 - play on easy while you figure things out, the betting handicap seems less
2 - if your horse is a dog, but just might squeak into the money, DON'T BET ON IT (literally, really) *
3 - when looking for horses to cheat bet, look for either solid winners, or long odd winners
4 - use vehicles that allow smaller bet amounts (long odds, E/W, the win or place accumulators)
* though when testing this out, I did try betting high on every horse likely to beat my horse. I felt like the reverse math mafia. Also, if betting no cheat, no look ahead. Look for horses dropping down in class. They usually haven't won in the prior class recently, so are put up as long shots and will usually win if not place. If the odds aren't greater than 4-1, E/W won't make you money either. So you get the best of both, a likely solid winner at low odds.
If desperate for cash and using the look ahead cheat, I don't like to crash my game much. Play forward a day. Note any horse that won by 2 3/4 lengths or more. Bet once on it to win if it did. One more bet for each added length. Note any horses that won, by any margin, but had odds of at least 10-1 or higher. Bet those E/W. Some days there are no betting opportunities, or just one or two. Then force close.
If you have two horses at the same meet that make the win, or e/w likely good bet list: bet on them using the accumulators. Remember that is "a bet" so don't bet on them singly unless that margin was high. If you do lose, you don't lose much. But when they pay it is nice. And since it is low money, you probably have it on hand. Betting this way, the takes should always be good enough you don't want to crash the game again and retry. Or if a loss, it is under £5k, and is fine.
Though, my preferred "bet" is on buying claimers. Is more of a US thing.