Spaced concrete paviors at least give you permeability (provided your sub-base and soil is permeable enough to let it run through) even if they *are* concrete.

Second hand bricks for me

If you spaced the "left over" Indian sandstone with bands of gravel - anything from 3" to 12" wide would you then have enough? You'd then have something that is relatively self draining, as Nick suggests, and could, if you like, plant herbs such as thyme or other low growing plants in the gravel. I'd lay a sheet of inexpensive weed barrier before gravelling and cut through it to plant.

Alternatively if you'll be using a table and chairs put the sandstone flags relatively closely spaced under this area so you don't have to think about whether the chair legs are going to sink each time you sit down (minor irritation) and put a wide gravel border around the edge.

wwwDOTpavingexpertDOTcom has some really useful paving info, incl a bit on SUDS.

In terms of mortar bed or not, have a look at how block paving is installed. It is all about edge restraint and compaction. If the edges are restrained (to a point below the sand bed, not just the bottom of the blocks), then once you have compacted the sand thoroughly nothing can go anywhere. It would be a bit more tricky with stone and gravel infil, because the sand could rise in the gaps between the stones, pushing up the gravel and making the stones drop, although if the stones are reasonably deep and you can get a couple of points of contact between each stone and its neighbour you may still be OK. You migt need a bit of mortar at the edges if you cannot get excellent contact with the edge restraint.

The peroblem with ''gravel around the edges for drainage and run off'' it may be ok, but less so if it's a small proportion of the 'hard' area - and remember that any amount of gravel will do little if there's clay or bedrock close beneath. You may need quite a bit of excavation. (Apologies if that's all teaching you to suck eggs!).

Nick

I'm with ST, crazy paving, may be a bit dated (think retro, it will be back in fashion) but cheap and re-cycled (in shropshire I used to buy broken paving slabs for £3 a ton collected) run off to a french drain and soak-away full of re-cycled broken bricks.

probably been mentioned already , but 2nd hand is your greenist choice , plenty on freecycle and free ads or auction sites. Conc. slabs or bricks are easily reusable if the mucks not to strong.
lay them on compacted sharp sand on a firm base ( made out of left over hardcore from project ?)