I need to get back my Google organic search listings

I have a small Joomla/Mijoshop Opencart website with Mijo SEF. My organic listings have been on page One of Google for several search terms.
My sales dropped off at the beginning of June and my web stats showed a severe drop in activity. My organic Google listings had vanished.
I went from approx. 120 clicks per day, then on 27th May they fell to 19 and now to approx. 6 per day.
I am still indexed with Google and have a product feed with active listings. My Robots txt is ok as is my Sitemap.
There is no indication of a Google Penalty and I can't see any Google Policy Updates.
There are listings on Yahoo and Bing and I don't think I did anything to my SEO to cause this.
I think the SEO URLs also need looking at.
My business is only small but I need the income.
I am totally confused and don't know what to do. Can anyone please sort this out for me.
http://www.posh-pawz.co.uk
http://www.designerpetshop.co.uk
Thank You
Kiana