Can anyone recommend a good 3rd party 500Gb SSD for a 15" Macbook Pro. The Apple ones seem a tad pricey.

cheers

15" 2.52 GHz Intel Core i5
10.7.3
4GB

OWC - http://eshop.macsales.com/shop/internal_storage/SSD/Mercury_Electra_3G_Solid_State

assuming your MacBook Pro is less than a year or so old, and can use the 6G-compatible devices.
Also, Newegg has a few...
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100008120%20600038519%20600038502&IsNodeId=1&name=480GB

Plus take a look at these installment videos (http://eshop.macsales.com/installvideos/) to see how to replace your hard drive with an SSD.