SEO Keywords - should I include location?

I am selling a certain type of product in the UK.
So - when I'm looking for SEO keywords to target using the Google Keyword planner, should I be including the term "UK" in the long-tail keywords I'm targeting?

Ie should the keywords I'm putting into the planner be along the lines of "buy product x uk" or just "buy product X" and, as one SEO adviser has told me, trust Google to know that I am in the UK, my site is mostly useful to customers in the UK?
Any help appreciated. I'm actually looking for someone who can give me a hand getting a few sites ranked and have a modest budget if anyone is able to offer some one to one help.

This is a point for debate, but few things are worth knowing.

Google can and does determine the target location of your website.
It uses a number of signals to do so including onpage location signals like pincodes, addresses and other factors like demographic distribution of ctr.

The subject itself is big and every site needs a unique strategy. I would recommend reading some of the tutorials on "google local seo" out there.