You can get a new car on lease similar to what OP is looking for at £350 a month which already is similar to the depreciation of a £30k 18-24 month old car that OP stated they were looking at.In the vast majority of cases, leasing a new car will be the most expensive option, whether you are an amazing investor or not. The vast majority of people are not amazing investors.
Then add investment return on top...
Put it in a tracker and don't try to be too smart

