Have ecommerce shop checked for problems

I run an ecommerce website and have had several reports over the past 72 hours from people claiming that they either couldn't get product pages to display properly or they couldn't add certain products to their 'cart'. The rest of the website (ie blog) has no problems as far as I am aware.

The theme is a Woo Comerce theme, and I use Cashie Commerce and Paypal for payments. I use Wordpress as a platform.

One person has claimed that they get the problem on their iPad.

I would like my website:

1) Checked for problems that may be causing this.
2) Identification of the problem (if there is one).
3) Suggestions for fixing the problem (if feasible I am happy to negotiate a further hourlie with separate payment).

You can view my website at http://www.londonherbgarden.co.uk