Changing to the newer car may seem like it's going to save you money in the short term, but after spending money on your Golf now, you will know you have got a good car under you for a good few years.
Your Golf will have done all it's depreciating, whereas the value of the Citroen will drop like a stone. If you buy the Citroen, in a couple of years time, it'll be out of warranty, worth bugger all and the chances are, it will need big money spending on it. The Golf on the other hand, may also need some money now and again, but at least it will be worth something.