Right, I've had three pallets of patio blocks sitting around since last
year, and I really must get around to doing something with them...

I'm assuming a layer of sand (about an inch) immediately beneath the
blocks (and a layer of weed matting) - then x inches of gravel.

a) What's a good type of gravel to use? ISTR local concrete firm
suggesting pea gravel (back when I was going to get this done last year
before the cold season hit and I ran out of time) - but I've seen others
saying that pea gravel is awful as a bed for patios because it doesn't
compact nicely (not to mention that it's not necessarily that cheap).

b) What sort of minimum/maximum thickness is sensible for the gravel?
Soil here is quite sandy down to a foot or so, then clay beneath that. I
think I've read "somewhere around 4 inches" in multiple places, but the
experts might think otherwise :-)

c) I assume I should slope it slightly away from the house to promote
water run-off; is there any good rule of thumb for the angle (fall vs.
distance)?

One gotcha is that the land also slopes slightly along the side of the
house; I think that even without any digging down that I've got a drop of
about 8" at the low end. I expect I'll need a bit of retaining wall at
this end below the outermost row of patio blocks - will a row of
interlocking bricks likely keep the gravel behind them in check, or
should I be looking at doing something a bit more substantial (e.g.
mortared together, and/or foundation, or using blocks that can be staked
into the ground)?

cheers

Jules