RhysH: You don't HAVE to find the £5k on your next one, you'll end up paying about £150 per month more (not taking into account any retail price rises that happen in the meantime) than this time if you don't though. You can take out solutions with no deposit, but it suggests about 10% deposit down. Worst case with GFV is that if the dealer was to offer you less than GFV on your next car in part-ex, you'd walk away from the one you have and start from scratch (assuming you have no excess mileage charges to pay).
It's swings and roundabouts with the monthly payment if you change every 3 years - put down significant deposit for a low monthly payment, or don't and pay much more per month. Alternatively you could put down a big deposit and pay more per month than solutions suggests to have a lower GFV to find if you were to keep it beyond 3 years (which will be saving you interest).
I reckon you'll start to see demo cars in aboout a month's time. If you want to order before then i'd suggest
taking out a MK6 GTI to get a feel for the performance and then a well equipped MK7 Golf GT to get a feel for the MK7 and the standard equipment.
There's not much in it between financing the depreciation on 2 concurrent GTD/GTI "ownerships" via solutions of 3 years each vs keeping one for 6 years (and paying up the GFV). 2 x £10k depreciations vs 1 x £17k depreciation (assuming a generous 6 year p/x value of £9k) + the cost of a 5 year extended warranty (for comparable coverage of 2 "new" cars)+ the cost of 4 new tyres extra wear (could be 6 = 2 sets of fronts and a set of backs)+ one more tax disc (1 each with the 2 new cars vs 1 with the 1 new car). At £150 per tyre, the cost between 2 x 3 yr solutions or 1 x 6 year ownership = £20,000 vs £18200, £1800 over the space of 6 years, or £300 per year extra. Don't forget that year 6 of option 2 has no warranty coverage.
Those are the kind of figures that VW engineer to make you want to change every 3 years, along with more generous standard equipment likely available in 3 years time.
I should be a VW salesman!