Dark Vader, I am in awe of your plan to run the SDW! I have the Harvey's map and used it on a walk from Eastbourne to Winchester some years ago. I don't know what your food plans are and how much you will carry, but I just wanted to say that the shop marked on the map at the village of Washington is no longer there.
My own little baby-ultra plan was to run the Avon Valley Path this summer from Salisbury to Christchurch (35m). Unfortunately we had those 6 weeks of rain leading up to my planned dates and the path was underwater in lots of places, so I postponed the run and will try again next year.
Dark Vader, I think you should consider yourself very lucky to be in the privileged minority. It is wonderful that your children will not leave university with a minimum £27,000 debt. The majority of potential graduates will be wondering how long it will take for them to pay that off over the course of their working life as they do not have parents sufficiently well off to pay their tuition fees or living costs while away at university.