Iain, I think that there would be a fair split of opinion as to what constitutes Solo Unsupported.
There are some real purist hard men like Glyn Jones from the Galloway area who did a solo unsupported Southern Upland Way, setting off with a 30lb pack that contained all the food that he would require for 6 days, plus sleeping bag and plastic bivvi-shelter - in Glyn's definition unsupported means not using any pre-constructed shelters ( sheep-folds, barns, bothies or your mate's van).
For my 50th I did a Scottish C2C (Stonehaven to Fort William - although some purists would say that Fort Bill is a good way up a sea loch and does not constitute the 'coast'; I was happy to dip my toe in tidal water).
I was definitely solo, but had posted food drops to the P.O.'s in Braemar and Dalwhinnie ( packets of Complan and glucose to mix with burn water en-route). I set off with an 18lb pack that included my Goretex bivvi bag, but also used bothies, bunk houses and youth hostels. I ate in cafes in Braemar and Dalwhinnie and raided the 'spare, abandonded food' shelves at the youth hostels. All my hill-going mates declared the trip to be 'unsupported'. I was not bothered one way or the other; it was a great way to celebrate my 50th and a memorable trip that really lit my candle; after all, I was doing it for me - no-one else!