Having tried a host of time tracking tools that are all ok, and do bits of what i need i have finally settled on Clockbase. Has every single feature i need at half the cost of a lot of the competition.
Easy to use, packed with features, excellent help.
If your looking for time tracking software, with features like, invoices, expenses, full project management then give it a try (it even has a two week free trial here - https://www.clockbase.co.uk/admin/register.php)