In Float it's easy to remove a budget from your cash-flow without fully deleting it.
1) Click into the figure you wish to edit
2) Untick the 'Include budget in cashflow' option.
This will remove your budget from the cashflow but keep it logged so you know what the budget had been before you ignored it. You'll see that once the budget is no longer included the budget options can't be edited. To re-activate these options just tick the include option and the budget will be included in the cash flow once more.
Remember: Float automatically switches from budgets to actuals at the end of the month. Another reason why Float will use an actual instead of a budget is if your actuals have exceeded the budget.