Buy both and protect your brand ? , It then all depends if you are totally aiming at the UK market ? if you are then use the .co.uk and redirect the .com to the site. Alot of people find that in the future they wish to branch out of the UK market and go global , having the .com too will allow you to do that with another site etc, By the time you decide that you want the domain in the future it could have been snapped up .
If you buy a UK domain means the bot will get to know that you are UK based and targeting UK people and it well get priority in UK search engines.
Yes very much agree with above suggestion and also have experienced and heard about such things. Why not buy both and keep the .com as well if its available now, who knows if it will be available in future or not. I would suggest to target .co.uk for UK business and also have .com domain with you. It can be helpful in future maybe for sure.
You can do that with any TLD by placing the relavent Meta data which will tell google and other search engines that your site is focused at UK searches.
What is this forum on??? The "World Wide Web"...let me emphasize the "World"...since domain names are so cheap around 10 USD it makes sense to purchase BOTH. As the World Wide Web expands our "customers" and our "market" will expand....why pigeon hole yourself with a UK domain name? If you have the option..... BUY BOTH!
I think it is better to purchase both! I usually like more the .com domains, maybe because I'm not aiming only to the UK.