Summary: It was crap.
Detail: Took about 10 minutes for me to realise the 1.5m3 bag I had bought was nowhere near close to what I needed. So I bit the bullet, and got a midi skip for £110. Which I filled with some stuff left over.
So an extra £20 over the Hippobag got me a proper skip ... begs the question what the target market for them is ?
Skip driver was not at all surprised to see the Hippobag on the top of the skip - it's not uncommon ;)
At least they didn't charge for collection in advance (although I can now see why they wouldn't. They'd forever be refunding).
With the nice weather yesterday, I finished the job, and took the remainder (mainly loads of MDF, glass bottles, and some paint) to the local tip. Was pleasantly surprised to find it quiet (usually queues onto the main road) and even more pleasantly surprised that the skips I needed were all in a row.