I've never had any problems with my spending limit. I too have direct debit set up. Maybe they are a little weary if you use it to purchase stock for business as it may not reflect true income. I think they are more comfortable with large spending on Travel/entertainment as it is more likely to reflect your true income (as it reflects disposable income). I'm sure if you normally charge £10,000 on Travel/Entertainment per month and increase to £20,000 (twice usual spending) the next, you won't have any problems