I'll be honest: looking at some clergy who appear to be overworked or overworking, it's not a pretty sight. Is it like King Lear who claimed to be 'more sinned against than sinning'? With regards to over work, are there genuine victims or can you bring overwork upon your own head?

I recently asked a load of full time clergy the question, and the responses ranged from 37 hours (that guy has is sussed) to 70+. Which is quite a range. I doubt many people count them up anyway; it seems a bit churlish. There must be a happy medium between clocking off half way through Thursday (which might be problematic for the congregation on Sunday) and working 15 hours a day six days a week, which, frankly, does not seem healthy.
Depending on what you read, 50-60 hours seems expected, but I haven't come across much in terms of Diocesan guidance. Perhaps I haven't read the right papers, or perhaps we're expected to be grown ups and, like teachers, just do the work. But even teachers have a notional number of professional hours, whether they stick to them or not.
Some Dioceses recommend a 'sessions' scheme, particularly with NSMs, who are by default part time. You divide the day into three sessions (morning, afternoon and evening) and work two out of three. This appears sensible at first, especially if you have something in the evening and could do with some commensurate down time, let's say in the afternoon. Realistically, though, more work can be done when you're fresh in the morning than in a similar length evening; evening commitments are much more costly in terms of energy and missing out on family time or, shock, horror, social life (if you have one). So the hours in a day do not carry equal weight. And if you start making each session into a set number of hours (I've head it's three in some dioceses, four in others) you could end up working 6 hours a day anyway, which is quite a lot of hours for an unpaid part timer. For a 'part time' clergy mum with school age kids this is all the hours in between school runs. And you still have the shopping/cooking/cleaning/washing to do.
Which brings us to the difficulty of knowing where work begins and ends. If you're at home praying for the parish, you're working, right? If you're in a traffic jam on the way to a church meeting, that's hardly recuperation time; it's work again. An assembly might only take 20 minutes but the preparation beforehand and the lingering in the staffroom afterwards could turn it into two hours work. It's why you need slack in the diary.

How long is a clergy working week? Should we even be asking? It's as long as a piece of string and as short as your next burn out dictates.