Just wanted to pop back and say thanks again to all who replied and advised! After nearly a week of nursing strike, he has finally decided that breastfeeding is back on the cards and is nearly back to his previous feeding habits. I'm still expressing at least once a day to maintain my supply as I feel it is still on the low side. Also ended up eating lots of oatmeal and using herbs to increase supply.
A few days ago I was pretty certain that I would never be able to get him to feed directly again and if it had not been for some of the responses to this thread I probably would not have persisted and kept trying. Exclusive pumping is hard work and my utmost respect to mummies who make it work!