Flexability is the key. 5 days is still better than no days. I love camping in the UK and only go further in a vain attempt to find better weather. I started planning this years trip down through france in Dec 07. Booking ferries etc is cheaper the earlier you can do it. I take the kids out of school a week early to get even better deals. Well worth considering as it can be a good saving.
I have just fitted an ECU chip and removed the EGR valve on my TD5. This is giving a 10% fuel saving at the moment so hopefully will cut the fuel costs down on my 2000 mile trip. I leave on Thursday. I'll let you know how it goes.