Are green manures worth it?

I'm just reading a Bob Flowerdew book and he thinks it is not a good idea to use rye or clover, for just that reason...difficulty of digging in.

He suggests mustard and phacelia as easier alternatives

I'm all for it. I sowed crimson clover after my onions last year and it got to a really bulky stage just before flowering when winter set in and it has overwintered fine. I was planning to chop off all the top growth and compost it, and then just dig the roots in. However I am just about to move to a new allotment so it will be somebody else's job now. I also regularly use tares and phacelia.

Yes - it's a member of the brassica family - was mentioned earlier on the thread.