ahh, bit of light building work, good for the soul.
I did one last year, took me 6 weekends to dig it out, smash up a load of bricks (which i found buried in the garden) for base and lay 140 slabs. the deeper the base, the better.
also make sure the tops of the slabs next to your house walls are at least 2 courses of bricks below the damp course, otherwise you'll get big problems - alternatively make a border with gravel around the edge it looks good, rain water won't splash up from it over the damp course (which it can from slabs) and if you measure it right you won't have to cut any slabs.
an angle grinder makes a huge difference to trying to use a chisel, but be a bit careful - i got one from wickes and the disc spins so that all the dust flys away from you, which is great until the disc sticks and it runs back over your foot..
Ouch,reminds me a bit of when i was putting a threshold board down for some patio doors in winchester,the drill bit snapped and went straight through my other hand.