Once again, thanks to all for the rapid and useful responses.
@hairbear Yes it is steep but I would be pulling not pushing because the large real wheels have to go first always, the little castors at the front would only dig in to the uneven ground.
Also I would envisage a few small ridges for my foot grip and a light braking for the chair. But:-
@Griffin36 those do appeal to me, especially as a permanent ramp has to take into account the fact that it would pass over the pipes to our fosse, not a good idea to isolate them completely.
However, even the ones I would choose, like you the 213cm ones would make it very steep. Perhaps married to a small sloping wedge of concrete at the bottom? This would also addresse the issue of anchorage as the steps are concrete with no obvious point of securing.
@Flocreen I haven’t read the whole of your link in detail but would I be right in thinking that it refers to public access, rather than private? Certainly @Griffin36 's ramps would be steeper.
@Corona & @Shiba Stairlifts and zigzags are not applicable, The first because they require a transfer from seat to chair and back again, something that is already very difficult because of lifting someone with a dislocated shoulder, and the latter because of the limitations of space.
The steepness of the gradient is only relevant to my ability to pull her up and down, nothing else, as she cannot even manoeuvre her wheelchair on the level, let alone a ramp. I think the regulations are aimed at invalids with a measure of independence.
I will ask Gill this evening and Christine tomorrow, also Carole who is one of the infirmiere soignantes who come daily now, for their opinions, but I am well disposed towards the long removable ramps. Especially as they can be used in other places and for other beings, ie elderly dogs who have difficulty getting in and out of the car. 
Again, thanks to all. most useful. 