I'm thinking of flooding here - if the patio is slightly higher than the lawn I assume it would not get waterlogged in a downpour - but willing to be educated! Thanks diymostthings
if the lawn is higher than the patio, it is easier to cut the grass because you can just pass the mower over it, if you are worried about water retention on the edge of the patio, lay a French drain (trench full of gravel) along the edge before laying the turf. A strip 300mm wide and 300mm deep should do it, cover stones in a one way weave membrane first to stop soil filtering into the stones.
Thanks Phil - sorry delayed response - travelling. Yes I was vaguely aware of french drains but I wanted to keep the patio as dry as poss and run-off from a "higher" lawn seemed to be all wrong. (water/mud etc.) I suppose if the soil level (not the top of the grass) was slightly lower than the flags, the mower could still go over the edge without hitting the stones. Thanks for your input - much appreciated as usual diymostthingd