I have been testing a coupon I setup and tried to apply a coupon to an order value which doesn't meet the minimum order value.

The error message that came up that specified the minimum order value was:

"You must spend at least £18.99 to redeem this coupon".

The source reveals that the page is attempting to render

£18.99

as opposed to

£18.99

On another note, the coupon was set to be valid tomorrow, and this was not mentioned when I tired to use it. I was being picky I would suggest that the valid dates be the first condition checked before other conditionals.