Like the others have mentioned, use either .com (which I think is king above all), then co.uk, and in the case that it deals with your niche perhaps a .tv. But more importantly, make sure it can pass what many call the over the phone test. Where if you were to say the domain over a phone someone on the other end could clearly understand what it is on the first go. And keep it short. The shorter the better. People don't have time to enter long urls and much less with smartphones.
Here's another tip. When looking for a domain in a niche. Write a list of short keywords that pertain to the niche. Then create another list of short keywords to complement the first list of keywords. Take those lists and use a keyword generation tool. You could find them online. What the tools do is that it just combines the words together (you could even use a spreadsheet too). Also flip the order. (example: keywords like london and media become londonmedia or medialondon). By the time you know it you will have a good number possibilities ready to see if they are available. Simply go into Godaddy's bulk domain search tool. You could plug in up to 500 at a time. Choose what TLDs to use (.com, .net, etc). And bam, you have a list of domains that might be available. Register the domains that you fancy. If nothing popped up, then rinse and repeat again. Something will show up. It always does. There are probably tools that already do all of this. But this is free and just takes a little time. Best of luck.
