For some reason when I try to manually downshift while on the move from 2nd to 1st gear it will not go into 1st. From a start it will allow me to stay in first if I move the gear selector into 1st and will then upshift to 2nd manually. Hope this makes sense...

 

Even after the road speed drops below about 15-20mph?

Cheers
DD

 

Manual shift from 2nd to 1st on a moving car is inhibited until road speed drops to around 15 mph, I don't know the exact figure. This is done to avoid damage to the box and drive-line and also prevent rear wheel lock-up if done at a higher speed.