Ok.. solved my own problem.
Adding the following code into your themes custom CSS will align the add to cart buttons on the product page while leaving other buttons in their correct position (including on other pages.)
/* This code aligns the add to cart buttons; leaving other buttons untouched */
.woocommerce ul.products li.product.woocommerce-page ul.products li.product {
min-height: 315px;
margin-bottom:10px;
}
#wrapper #content a {
position: absolute;
}
.woocommerce ul.products li.product .button {
bottom: 0;
vertical-align:bottom;
margin-bottom: 10px;
}