Posted: 22/04/2015 at 11:29
I hear what you're saying Emma lou, but if they walk they're in breach of contract and you should take them to the Small Claims Court (very simple).
The work is being done for the price quoted - if they made a mistake in their calculations that's their problem and not yours - they'll be more careful in future, but you should not be the loser.
The soil should be suitable for the purpose (it very obviously is not) and the plants should be of a similar size to those in the illustration unless there was a written proviso that smaller plants would be used.
Stick to your guns! We're behind you