You need a recessed manhole cover like this http://www.pavingexpert.com/recess01.htm
I have existing old concrete and wonder could I break this up and use it as a rubble base? Any ideas how I break it up without the use of a power tool?
That's hard work Colette but you can do it with a sledgehammer- I know- I've done it! Depends how thick it is- what you need is some healthy fit young boys to do it for a few beers!
Pretzel if you're still around- I just read your post re wooden pegs. What you do is get a piece of nice straight timber and tack it between the pegs and put a spirit level on it. Do that across the whole area you're trying to lay out. You can do it with a string line too but you need it to be really taut and getting a helper to assist is useful.
Thank you fairy girl a man that can is coming tomorrow