Best approach to retain raised patio

[Selfbuildnewbie]

So our house is done and we've moved on to the back garden.  The house is on a hill which slopes down away from the house, and from right to left as you look at the garden.  The back of the house is elevated above the garden.  We wanted a patio/seating area directly outside the back of the house, without steps and trip hazards, so a raised patio has been created using Type 1  so that it's flush with inside floor levels. 

 

The only issue is that this has exarcabated the extent of the fall from the patio to the rest of the garden, and with toddlers and elderly parents, we don't want any drops off the patio (and we don't want building control to come along and require us to put in railings).

 

The solution to this was to (a) increase the level of the lawn slightly so that the garden more gradually steps down and (b) run a sloped flower bed from patio level to lawn level.

 

How should we be retaining the hardcore for the raised patio?  I came back from a few days away and the groundworkers have used concrete to retain the hardcore (referred to it as concrete batter...).  See picture below.  Is that going to hold in the long run or should I be insisting they retrace their steps and put in a vertical retaining wall with gabions or concrete blocks?  I want to be pragmatic at this stage but obviously don't want my patio collapsing at a later date!

Side on view as currently is: 


The plan (raise lawn height slightly and have sloping flower bed from patio down to lawn)

 

 

What they've done to retain the hardcore  (added concrete to slope to stop hardcore slipping).  Below the red line with be infilled with subsoil + topsoil to create sloping border down to the lawn.  Lawn level will be roughly half way up the wooden posts.

 

 

 

[Mr Punter]

The bit where you have "infill with subsoil" is now concrete.  Do you intend to get rid of this?  I think that without steps, the slope will be too steep and the lower section of garden will be fairly redundant.

 

Gabions may have been better to retain the patio, but that ship appears to have sailed.

 

If you don't want handrail you could have some planting at the top.

[Selfbuildnewbie]

@Mr Punter  There is a slope/steps down from the patio to the lawn and lower parts of the garden.  It will be behind where I was standing when I took the photo.

 

If I leave the concrete as is, then we'll just infill above that with soil to create the sloping flower bed down to the lawn.  The concrete won't be seen.

 

They did the concrete without discussing with us so, if there is a strong reason why we should do gabions or other vertical retaining wall,  then I'll go back to them and see if we can retrace steps to do it properly.  But if this concrete is sufficient and will hold long term then I'll probably leave it at this point as it'll be hidden once we infill with soil.

 

This is a birds eye view of what we are trying to achieve. When I took the photo i was standing roughly where the garden path meets the lawn, facing the circular patio

 

 

 

 

Edited July 22 by Selfbuildnewbie