Congratulations on choosing a 500. IMO the 1.2 is a great all-round car.
You will naturally be very enthusiastic when you go to collect it and it's important not to let that get in the way of giving it a very thorough checkover before parting with your cash. Be particularly vigilant in looking for panel damage and any signs of panel repair - if you find the latter, I'd suggest you just walk away.
Hopefully all will be well and then you can concentrate on enjoying your new purchase.
Yep - don't worry - I plan to pick round it very closely! I know that it should basically be IMMACULATE given the age and mileage and I won't settle for anything less.