Blip has just used her ramp and cat flap for the first time
She was asking for a treat so I took her outside, came back in myself, shut the door and lay down on the floor next to the cat flap, holding it open, with a dollop of tuna in a bowl in my other hand. I passed the bowl through the cat flap a few times and Blip drew closer and closer to investigate. After a great deal of hesitation, Blip finally launched herself through the flap
So, her microchip has been learnt and the flap will now open inwards for her and no other cat. The next stage is to get her to use it regularly but as she's got the hang of it, after a fashion, within a few minutes, I am, provisionally and cautiously, optimistic.