CGT is already payable on second and subsequent houses, also on art and watches, indeed most personal possessions other than cars. No CGT on the sale of primary residences but the Government eventually gets that via IHT.
I stand partially corrected, I thought art was CGT exempt, but it's still only taxed at 28% if you hold it for more than a year.
According to this, watches are exempt
https://www.gov.uk/capital-gains-tax-personal-possessions/limited-lifespan
