Some info on VAT and National insurance

Hello to all, please give me some info on VAT and National insurance

My wife and I are moving down to live in spain in the new year, we are only renting, we do not have any great amount of money to take with us, were coming down to be close to our daugter. In the UK I sell used clothing at car boots and markets in town centres, I do not need to reg for VAT in UK because I never go over the threshold to have to pay.

When we move to Spain, I will be simply selling used clothing at car boots and markets, will this mean I will have to collect VAt.

If Yes, If I rented a small lockup unit in the uK, and then moved to Spain to live only, not to work, and then sold my used clothes on online auctions in UK, and got someone to pack and send my orders out from the UK, I would not have to collect VAT or pat income tax in Spain would I ?? my aim is to live in spain and sell my products from the UK to the UK like we always did.

Could someone let me know could I work this, this way, if not what would be the best solution, I would rather pay national insurance to UK and stay self employed and pay tax to only the UK like I have for the last 20 years, but now ten years away from UK state pension wish to live in Spain.

thanks very much for reading and helping me with this