I don't have any fixed hours in my contract

You  still have the right to be paid a minimum hourly rate of pay during your notice period for any time that you are:

• off sick
• on holiday
• temporarily laid off
• on maternity/paternity/adoption leave
• ready and willing to do a reasonable amount of work to earn a week’s pay, but your employer does not give you any work

Your pay during these periods is worked out by dividing your average week’s pay by the number of hours you normally work

What if my employer won't pay?

By now you will have a full case history of everything that has been said and done about your own circumstances.  This should include letters (either snail mail or e-mail) from you to them saying that you have not received what you believe you are entitled to.

Use your case history and refer to your organisation's grievance procedure.   Follow the process to the letter - any shortcuts here will cost you later.

If you and your employer still can’t resolve the issue then you might be able to make a complaint to an Employment Tribunal for breach of contract.

Pay instead of notice

Sometimes it is in both your interests not to work out the rest of your notice period.  You can agree with your employer that you can leave as soon as you are given notice in return for lay in lieu of notice.  This is often called "gardening leave".

You should still receive your full entitlements as if you were working out your notice.

This link takes you to the HM Customs web page, explaining the tax implications

Tax on pay in lieu of notice

Note that if an employer dismisses you without payment, then the employer is in breach of contract and you can sue for the wages that you would have received if notice had been given. 

Some employers are prepared to pay this sum gross, rather than net, but entitlement depends on the contract of employment.