(One view. Helpfully unencumbered by any actual facts, of course.)
In haste - an interesting take that I'd missed from the BBC's Mark Urban. The main point is that UK seems to have had a negotiation fiasco - the idea of bouncing the rest of the EU into something unrelated to saving the euro at a day's notice was always going to be difficult, and in fact it was a shambles. Fortunately, the UK is walking back on this at this point.