Conflicting advice on drainage and soil
We're planning on removing the paving and slate chips of the house we've moved into, with the hope of laying turf and raised beds. However, I've received conflicting advice from 2 professional gardeners.
Our garden is flat, 9m long X 4m wide. We're in London, so it's a thick clay soil and it faces North North East.
Ok, both gardener A and B suggest putting the garden on a slight slope when we lay topsoil, so that rainwater can run back towards the house where there are French drains at the patio.
Gardener A said to excavate down 20cm of the current matter which is sharp sand, before we lay topsoil. Thankfully, there was no builder's hardcore. Gardener B said no need, as the sand will help with drainage. This one is important because it either involves a lot of digging and large amounts of waste removal - or not!
Gardener A said lay a channel drain under the soil (I am clueless about these - where does the water end up?). B said no need.
A also said to mix some compost or manure in with the topsoil to condition it for drainage. B said no, turf is best without compost as it's too crumbly.
Finally, A said to get a fencer to add gravel boards before we have the topsoil delivered, and B said to affix them afterwards.
Can anyone help? Both are professionals! Thanks