I finally figured out what i've been doing wrong.
I brought my horse back into work about a year ago, during that time i've been focussed on him and how he's progressing, so focussed in fact that I forgot about one of the important parts of riding, the rider!
Recently I took video of me riding in the hopes that I could see where I was going wrong and if I could fix it, I posted still from the video on the forum and got some really great advice.
Yesterday I rode for the first time in about 2 weeks (bad weather stopped me riding as our outdoor was really slippery) and decided to focus completely on me and my position for the entire ride. I pulled my leg back, had a good contact with his mouth with my arms in the correct position, tried to use my core muscles more and actually looked where I was going. It was like riding a completely different horse, Phoenix came off his forehand, lowered his head and actually listened to me. He was a little fast because he's been a pasture potato for two weeks but I think that helped, because he was going and actually forward for a change he was giving more from behind and was going on the bit for the first time since I brought him back into work.
I was so pleased. Something so simple I wish i'd videoed myself a year ago.