Personally i can't suggest anything for you to step into as im already away to embark on my 3rd career change but this one will stick as i enjoy it and can get the relevant qualifications quite quickly.
However i do know, make sure that you have a good plan that you can work through and don't go in over your head. The most important thing is to manage your cash flow. Don't go straight into the deep end and make sure you can keep yourself goign otherwise it will just get worse. The bank are your friend and don't be scared to speak to them. They are willing to help you. They want to keep your business and keep you going in the right direction as that makes them money in return. But doing what you have done, im sure you are more than aware of this.
For what you decide upon, make sure you have it planned correctly.
Make sure you market to the required customer base and not someone who wouldn't be interested. No point in trying to sell skateboards to old woman!
E.g If you want to be a net business, what happens if phone line goes down? Do you have a backup system in place like dial-up etc.
Even starting small and you start to get somewhere and you think your turnover will go above £56,000 during any 12 month rolling period then make sure you are VAT registered or otherwise face a stiff fine or whatever else HMRC can conjure up! For any 12 month period you must monitor it or HMRC might come a calling and their bite is far worse than their bark! Helps if you don't have a dodgy accountant 😉
If you do decide to go ahead with this then good luck 🙂