Option 5 - px against the car you’re after with whatever form of finance you can get at the most suitable deal for you.
Being on a PCP doesn’t actually limit your options in any way.
Obviously just hanging the car back and walking away is a dumb thing to do. If yours is worth £29k and you’re looking at a £25k car then you’d only have to find £15k which shouldn’t be difficult to get at a good rate.