Hi hun
To be honest I'm not an expert on this subject but I've learned the following info over the past few months as I've only been self employed for the last 6.
OK - you need to contact the tax office in your area and advise them that you wish to continue paying your stamp- this should be done within 3 months of you starting yor business, as Gill has already stated.
Did you know, as you are on 'low income' you may be able to claim 'working tax credit'? As this is my 1st year, I am actually running at a loss at the mo. It will take a while longer before I'm in profit so I'm in the process of seeing what benefits/tax credits I can get. The helpline for England, Scotland & Wales is 0845 300 3900. Give them a call, they're quite helpfull. They will send out a form for you to complete.
I went along to an accountant and asked what information I need to supply. I'd entered all of my outgoings, i.e. what I'd spent to set up - stock etc into an Excel spreadsheet and reconciled all of my receipts. Keep all of your receipts hun, even petrol ones. My accountant informed me that what I'd done so far was fine and I was to wait for the tax office to send out a tax return form, then to take it to him - bonus!!
If you Google on 'setting up new business' you'll find loads of info to help and, of course, do a search on this site too!
Hope that helps.