It sounds like you have enough money now and incoming that PCP might not really be for you. Why not use the deposit to buy outright with a bank loan with lower APR to cover the difference? When your windfall comes your way you can then pay off the bank loan right away with no penalties.
Also think carefully if that new car smell is worth the extra cash. Depending on what you're coming from, a nearly new from a dealer would save you a fair amount of money for very little difference in car. From my experience buying a 16 plate GTI PP this year, the whole thing felt exactly the same (actually, better) as when I bought a new TDI 4 years ago - but with far less waiting around.
Depends what you define as "nearly new". For people who'll keep a car for 7 years, 2.5 years old is "nearly new", for others it'll be a pre-registered car with no more than a few thousand miles on the clock.
Most people on this forum buy new and are ready to ditch about 2.5 to 3 years old and get on another PCP.
My experience with performance VWs (i'm on my 9th VAG car) is that 13-15% discount without generous deposit contributions (a very recent VW incentive, never before seen it on performance models until about 3.5 years ago), and maybe 20% with deposit contributions. Compare that to a year old model that VW have up for 85% of RRP on their used forecourt with few or no incentives, 50% higher APR rates than new cars get and many will struggle to see any plus points in getting the used one.
Go for a 2.5 year old GTI/GTD/R for 60-75% of RRP, shortly needing some new brake pads, discs or tyres, a short warranty and about to need the annual MOT for the same monthlies or only a little less - i'd rather be getting new.
The way performance VWs hold their value it doesn't make much sense in most circumstances to get a nearly new one, but for other marques with horrific depreciation, it makes little sense to buy new, when an 18 month old example will still have a big wedge of warranty remaining for half the RRP.
If you do want a cheap bank loan, the best way to replicate PCP terms with APR% savings is to take out a 5 year loan with the intention of settling up at 3 years to start again if you change your car every 3 years. What's left to pay at 36 months will amount to a low balloon payment, ensuring that you will be in positve equity vs what it's worth in p/x.
Dealerships receiving a car beyond 2 years into a PCP will usually guarantee to get you out of negative equity with their p/x offer. It is in their interest to offer you something as a hook into the next car rather than you having your options wide open to walk away at 3 years because there's no positive equity to make you want to stay.
In the past, I have generally seen around 10% over the GFV when trading in, when I was PCPing. To know if you're being offered a poor deal, aim to get around 85% of the sticker price for pretty much the same car (same age, trim level, mileage) on their used forecourt - they will always want to make money on your p/x as well as the new car!
Offloading the wife's Audi A1 recently, I found Autotrader a complete waste of £50. I was selling her car with lots of options that the competition didn't have, and half the mileage of most of the pack and certainly the lowest by 10k miles for A1s of the same age and engine, and was the cheapest by £500, I had an extended warranty that no-one else had, and I got no bites. No-one has money of their own to buy a car with at the moment it seems - they all go to the dealership, so I wouldn't buuy a car thinking that i'm going to get £2k more selling privately than take the p/x.
In the end the local Audi dealership took it for £800 less than my Autotrader price. Figure in that someone is going to want to chipyou down by £500 or more and it ended up being a fools errand.
My R has held up well in price. I have just agreed to p/x it against a new Polo GTI+ (this will be our second), and at 3.5 years old, the p/x value is coming in at £17.5k, with a £300 depreciation for every month thereafter until the Polo arrives. I paid £28k for that car, so for me to be offered 62.5% of what I paid for it new at 3.5 years is by far the lowest % depreciation I have ever experienced on a new VW. It would be on their forecourt for £21-22k right now, no way I would pay 3/4 of broker price for a new one to get a 3.5 year old example, but clearly someone would buy it at that price for it to be selling for that price.