Sandstone patio

I have an existing patio (circa 35 Sq Mtrs) comprising sandstone flaggings, which over the years (1929) have sunk and look absolutely terrible with gaps filled with as much as 3 inches of concrete. Some of the flaggings are quite brittle given their age but I have a plentiful supply from other parts of the property. I have no option but to pull them all up and relay them but before doing so I must first clean them (smooth them off) and cut them to have four straight edges (not necessarily square or retangle). I've bought an angle grinder and a $169 diamond grinding wheel, which does the job but a) it's very time consuming and b) backbreaking. I thought of hiring a brick saw with a diamond blade from Kennards but they want $281 per day plus $110 for every 1 mm of wear on the blade and being sandstone they say that is the most abrasive material to cut so wear and tear will be heavy. Does anyone have an alternative way of doing this?

I used a $99 Ryobi tile saw to cut sandstone, ceramic and polished granite tiles. The blades that came with the saw lasted no time but I replaced them with one that cost about $25 and it lasted almost "forever". I did have to replace it towards the end but I couldn't have been more impressed. I started wet cutting the sandstone but that was pretty messy so I just dry cut everything after that.