The second stage of the Amateur radio licence is the intermediate Licence.

It allows operators who pass this exam to operate on some bands at 50W. but it is more of a commitment than the foundation Licence and a much longer course.  You have to have passed your foundation exam before you can sit this exam and there are some practical assessments involved so you will need to visit a club for at least some parts of this exam.

Please see the RSGB site for approved training centres in your area to arrange your course/exam.