No. If you sell one car it would be assumed to be the normal sale of a private car. And even if you make a profit, it's not taxable because it's not trading income (you're not a car trader) and it's not subject to Capital Gains Tax (tangible moveable property with expected life under 50...
One of their more sensible rules (possibly the only sensible one they have brought in, in the last 50 years!) is that if you have a small business the first £1,000 income is effectively tax-free because you can declare £1,000 of expenses withot paperwork and without question. This was...