I only have my high school diploma and work in a call centre/admin background. Not very unique and not someone who stands out - normally. Work can be found (I've been interviewing for about 16 months, temping in between, just unable to actually land the job) just keep looking. Being in a large city like London, I think its easier to find work if youre not uni/college educated than it is in smaller cities.
As you're someone who has run her own market stall, you have management skills, inventory and sales experience, with loads of customer service skills. I wouldnt say thats someone who isnt desirable. Once you move here, you WILL be someone who has worked abroad and that is desirable for people.
As others have said, I would investigate whats missing from the markets to the area youre moving to. If whats missing is what youre already doing, you can probably set up one of your own (and some areas markets are indoors!) and be working for yourself again. England, especially working and middle class England, love their markets. I prefer shopping in ours for fresh meat and veggies. You can find some steals on some of the stalls for clothing and antiques as well.
Yes youre worried about giving up your safety nets, its one of the downsides of moving abroad. If stressed, once you do get work, try keeping some money to the side, so if need be you can get back home and set yourself back up again.
It will be okay no matter what YOU decide to do.