I had this problem last year. I lost the client, but I was not really bothered. I started the contract in November, the place was a mess and I personally put in the extra hours to get it up to scratch. But when Christmas shutdown came, he refused to pay, stated that there was two cleans missed and he should not have to pay for that. I showed him in his contract where it states that all shut downs are taken into consideration of the quote, but he still was not having it. I told him that I still have to force my staff to take holidays or unpaid during that time which means they would have to take their holidays during another time and I would have to provide cover at my expense, he still was not having it. He even pulled over my staff and asked them a lot of questions, like did you get your full pay during the holidays, which of course they replied yes. And still he was not going to pay, he said he did not care what the contract states, he was not paying for a service he did not recieve. If I intended to charge him he would terminate the contract right away without regard to a notice period. Losing that contract was one thing but what really bothered me was that he was the Master Franchisor for two other contracts that I held. But I stood my ground mainly because if something as small as this would actually stand in his way this much, how would he react to something else. I decided it was better to cut ties with him. I called him personally, and made him feel pretty small. With the cost of a court proceeding not to mention my time I did not want to pursue the matter. I did let him know that it was not about the contract it was about integrity and doing the right thing. I told him he was more than welcome to rip up the contract as I refused to conduct anymore business with him. The other franchisor that I have the contracts thought it was pretty funny in the end and knew that he deserved it. I still have their contracts to this day.
Saying that I have new contracts this year and I have just sent out my invoices so I will see how it goes this year. But I do not think any of the old clients will say anything, as I said it is in my T and C's that any shut downs are taken into considration. If it was a customer that I wanted to keep it would be a little harder issue. One thing I did last year after the incident, and only for the two franchises was I told them maybe I was not clear enough on the issue and I lowered thier monthly price by 3% which makes up for the closures, and I am still able to budget for holiday pay. I think it was 3% but if you do the math you will find it is not that much of a difference and the client sees it when you lower the price.
I hope this helps a bit.
Gilbert