Question about National Insurance in the UK?

I am in full time employment, paying National Insurance out of my salary each month. I also do occasional freelance work, but have to pay class 2 National Insurance every week too because of this.

What is the reason for this, surely I'm paying twice? The freelance work is only a top-up income so how come I pay the same N.I. as someone who relies solely on self employment as well as the amount that is taken from my regular salary?

Yes, I'm also registered to pay tax on this additional income, but I'm not sure yet whether the amount I earn will add up to more than 拢4465 in a year, so if it doesn't I'm hoping some system exists to refund the N.I. I have already paid...?

Speak to the accountant at the firms you work at.

Class two contributions are paid where a person is self employed and is 16 or over and under state pension age. Contributions are paid at a flat rate of 拢2-10 per week regardless of the amount earned. However, those with earnings less than 拢4,465 per year can apply for a small earnings exception, e.g. exemption from liability to pay class 2 contributions.

This is a detail from the document below. It goes on to state voluntary contributions called classes 3 and 4.
It is quite lengthy (too long to type out here!) but not too difficult to understand. Your local lending library will have a copy for you to view and photocopy if you wish. Do it this way and you'll know you are correctly informed.
Good luck! DB

p.s. Be careful -are you paying tax on your freelance work? Even if it's minimal you still need to quote it as self employed tax. It's a pain

You can claim exemption from Class 2, but you can't reclaim NICs you've already (mistakenly) paid.