Understand your broadband.
If your Internet Service Provider (ISP) support team are telling you that your line is fine, and everything is working as expected, you may need to do some homework about your service.
Understand what your maximum speed is
Standard broadband over telephone lines degrades in speed the further the line is from the telephone exchange (in cabling length). While most deals are advertised as 'up to 16Mb', most telephone lines will be rated to achieve slower connection speeds. Run a broadband speed test on your line. Ensure that the speed you're told to expect is actually higher than the speeds you're experiencing - it may be that you're already achieving the fastest speed your line can expect no matter if you live in Plymouth, Yelverton or Tavistock,
Check your download allowance
Make sure your ISP hasn't capped your speed because you exceeded the limits of your monthly usage allowance or traffic management policy. Many ISPs now reduce your speed rather than charging you for exceeding your allowance. You should be emailed a warning if you exceed your usage allowance, however if you've simply exceeded the traffic management allowance (often in place at peak times) you won't be informed, your speed will simply drop for a fixed number of hours (or until the peak period ends). Your ISPs website should give you details of any traffic management policy in place and inform you of the effects of exceeding your usage allowance.