I've entered the Super Randonnee, for a date in August. With 60 hours to complete the ride, it'll be like the Mille Cymru Grand Tour, where tough days are interspersed with a reasonable night's sleep.
I'm planning a leisurely 8am departure from Knighton (giving me some extra daylight on the final day), finishing day one at 200km in a pub in Llanidloes. Day two will be a further 200km, which would take me to Llanrwst (on the way back from Llanberis). I can't find any accommodation there, or anywhere on the route for the next 50km. There is a campsite just outside Llanrwst though, so I'm thinking I'll need to take some minimal camping equipment with me. That'll add to the challenge! Then back to Knighton by 8pm on day three.
Food options appear to be good for most of the route. The only stretch where I need to investigate further is the leg from Llanrwst (where I will aim to leave the campsite at 4am), through Denbigh and Mould to Llangollen. Arriving at Llangollen around 9am so should be able to find some breakfast then, but I'm hoping there will be a petrol station or shop open before then on the road, preferably around Denbigh. There appears to be a Co-op in Denbigh open at 6am on a Sunday, so that might be my best option.