Simon

If I remember your videos your had a really good takeaway but your lower body collapsed on you a bit (right leg straightened .. no coil) and you overswung and went across the line

The inside of the right leg is key. If you cant feel a stretch in it half way back then IMHO you arent coiling properly or have swayed or like in your case back then, you didnt really have any coil and were just going up with the arms. I havent seen you post a vid lately so I dont know how youre getting on. Great I hope

I find that if I kick that right knee in which also rock the hips up a little toward the target then this really helps me feel that coil as I go back. From that half way position you can hit the ball well but you can also lift a bit from there too (right arm bicep curl) if you want more elements of a Two Plane Swing (which is perfectly fine)