A National B Competion Licence is all that you will require Neil and you can get that at Knockhill.
If you are planning to progress then you will require very deep pockets indeed.
Here's some rough figures to give you an idea of what you might have to spend:
Club racing £5,000 - £30,000+
Semi-professional £60,000 - £170,000
BTCC, F3, British GTs £250,000 – £500,000+
These numbers are per annum
To get to be the next Lewis Hamilton... £5,000,000 (no guarantees!)