Don't!! It doesn't matter if your ebay account is a Personal account - but a business account is not worth the hassle. (or lack of ebay promo offers)

If you upgrade to an ebay Business account you won't be able to change back & you may (& probably will) miss out on any ebay promo offers.
eg. Free Listing/free FVF that is currently on offer.

I was talking to ebay yesterday about downgrading one of my 'other' ebay accounts to Individual due to the business winding down...

It's not going to happen. That ID never gets any promo offers...