Its all about the numbers. On PCP in the past I have traded in a car I own and it has been over the maximum deposit for the car I want. In three separate cases the dealer gave me a cheque back for the difference, I got £2.5k back in my hand for a volvo I traded in against my mk2 Leon.
When it comes to your next car you can try and sell your old one private, Im not a fan but Ive done it. Or you can cut your loss and palm it onto one of the car buying places. I currently have an ex PCP that I bought at the end of the term and have 7k tied up in it. The value seems to be going nowhere and I estimate its straight sell value as just under 7.5k, forecourt price for worse is well over 9. I'll be looking to sell it in a few months and if I can get my 7k back I've had a car for free for a few months. Im looking at a lease next anyway so trade in isn't really an option.
Lastly, if you are looking at the new Octavia, then I wouldnt worry about 500 quid here and there, the price of the new models are very high. The SE edition, with some extras is over £26k for a manual 1.5tsi. Best discount I've had so far is £2k off that, which makes it more expensive than my DSG 245 VRS was. Also, someone earlier was talking about discounts on cash buys, if you look at the deals the PCP is cheaper on paper because of the interest thats not included on the initial price. The key to getting that discount when buying outright is to take out the finance to get the PCP discount and then pay the finance off at the earliest opportunity!
Also, another last thing, I've been the guy who has bought the first version of a new car and sworn I will never do it again. I paid SEAT a handsome price to be an unwilling beta tester on their mk3 leon. Im not doing that again, especially for an SE with the wrong engine and gearbox 🤣