I'm usually in favour of people (especially people without other commitments and responsibilities) doing rather 'out there' things to get into their dream industry, but I am not sure that your plan is going to work out for many of the reasons given in the thread already. Unless this is a temporary dream job of a few months' duration where you'll be moving on before winter, otherwise you are just going to continue to have worse housing issues in the winter and your CCJ will stay on your file for 6 years from when it was put on there unless you can get it removed, so this is not a temporary problem.
You could ask your new employer if there is anyone in the company or that they know of who would have a room to rent (do not say "tent to pitch" or anything about your car and beware that in this rural area news may travel fast about enquiries about the tent or rooms (no bad thing) but also if have been seen or heard talking about sleeping in your car, which may go down less well.
You should ask every hotel, B&B, landowner, farm and campsite in the area if they have a space for (your car?), your tent, or any pokey little room e.g. with a non-ensuite or that needs improvement, that they are currently not letting out but would let to you.
<strong> >>Not everyone is online!! << </strong>
People often like to meet the person they are thinking of renting to or helping, to size you up. Put up cards in local shops and use word of mouth as well as social media and room renting sites. Write actual letters to put through doors, gather some character references and previous landlord's references in both email and paper format for accommodation, do the same for your offer as well, and carry them on you ready to hand out when you are approaching people who want to know more before considering. Be careful with cold, damp, mould, fire though, of course, don't take somewhere that is unsafe.