SJ- I re read your post a couple of times, and I would venture that the company has no money.
The old, and we use it in one of our business's, is pay all outstanding invoices, and get your deposit back. If the invoices are not paid, we deduct from the deposit, leaving a balance that will be returned to the customer. However, no one likes giving back deposits.
In theory deposit amounts SHOULD be held in seperate account, but reality is that they are used for cash flow. So, when to be returned, guess what, no cash in bank, and up to overdraft limit.
You have now paid them an extra 210.00, which with hindsight, I may not have done. Therefore they now have 660.00 of your dough.
Pay them a visit - the door step call is generally a winner, failing that CCJ route I am afraid, but that can be fraught, and is not always a result for you.