I used to ride with my toes pointing out and my trainer would always point it out to me, I found it easy to stick them in and remember at walk but then at trot and canter I forgot, it took a few months and when I first started to remember my ankles hurt but after practice and time I just automatically point my feet forwards and they look fine and it doesn't hurt one bit now. So just try to keep it in mind and with time it should get better and won't hurt.
Thank you everyone for all your advice, I shall be having some good old position practice on Monday :) I'll do some no stirrup work as unfortunately my stirrups are at their longest already...
I think my hardest obstacle will be understand how to "hug" with the inside of my calf, yet not pinch at the knee... I'm struggling to see how I'm going to do this, but I'll try really hard!
I did attempt to keep my toes pointing forward during my lesson last night, but I may have been doing it wrong as my ankles were very very sore the whole lesson.
Is it possible to punch another hole in your stirrups? One of my friends has really long legs and had to do this.