Hi Snoops
I'm a bit out of touch with prices but expect £70/sq.m and upwards and take heed of Fred's Dad. He is spot on with his comment about correct site preparation. You will only get what you pay for in this world and you will find prices or quotes will vary dramatically. I've seen lots of block paving over the years and sadly there are more bad examples than good ones.
Besides getting a good foundation there are others variables to consider.
Edge restraint is possibly the most important since any movement here leads to progressive loosening and movement of the whole surface.
Where the blocks are against a wall, building or kerb edge you will be ok. Any "free" edge ideally needs a kerb race underneath it for peace of mind.
On top of this other variables are the block type, thickness and tessellation pattern.
You can have square blocks, rectangular blocks or a mixtures of the two, generally known as tegula.
For domestic use 50mm blocks are acceptable but are more prone to cracking under point loads (eg car jacks and axle stands)
Herringbone pattern is generally regarded as the best for surfaces carrying traffic and a good contractor will never use less than half a block.
Once the blocks are laid it is important to keep the joints full of jointing sand, well compacted and free from weeds. Failure to do so results in destabilisation and movement of the blocks leading to settlement. Pressure washing is very good at destroying block paved surfaces!
Although it can look nice, I think block paving is seriously over-rated and far more trouble than it's worth - and it's not cheap.
Have you considered a concrete imprint solution? This is more forgiving of an uneven sub-strate and yields a single cohesive surface with little opportunity for flora to propagate.....
Hope this helps
