The Panda series of updates, launched last year, targeted poor quality content and can affect your Google SERP rankings if you have issues with the quality of your content. Sounds like you are good there, so no worries as far as Panda.
However, this year Google launch another update labeled Penguin. The Penguin update targets webspam, so as long as you are using purely white hat SEO techniques you will be fine. Sadly, some folks seem to think that the only type of SEO is webspam, which is certainly not true.
As long as you are not creating webspam, keyword stuffing, using hidden text, or other black hat methods you will be fine. Meritorious link building is still important, especially if you are in a competitive niche.
As far as ranking in the UK, it helps to have your UK address featured prominently on the website, and you can use schema.org to help search engines better understand your website, including location.
Rich snippets – Organizations – Webmaster Tools Help
Also, you may want to look into PPC advertising, which is almost always a good idea for eCommerce websites. PPC will get you tons of targeted traffic straight away, and you can use the profits from your PPC to fund a really big SEO campaign. Hit the competition from both ends.