The Brew Cabin

What a great site!
I was wandering if it would be o.k to use dry sand jointing with a stabalising solution after bedding block pavers on a rigid construction, by laying the pavers on the mortar bed and leaving the joints for later?

You're sort of caught between the two - rigid paving requires rigid bedding and rigid joints, while flexible paving - you guessed it - relies on flexible bedding and joints.

Combining a rigid bed with flexible joints is a bit of a mish-mash and you'll probably have problems with block movement over the longer term, as the joints won't be strong enough to resist lateral movement which therefore imposes the whole load onto the bed-block bond. This bond relies on the adhesion of the block to the bedding and is likely to fail (break) if severely tested, as it was never designed (strengthened) to cope with such loads.

To put all this into layman's terms, the blocks will probably start to come loose. It might not be this year, and it might not be next year, but bit by bit, you'll begin to notice that the blocks taking the most loading, such as those in areas where the wheels of the cars are turned and those on curves/arcs/radii, will start to flick loose.