Yes, I did exactly as I was told 15 mins warm up, and as luck would have it a route with 3 fairly tough hills, the last being the toughest and that was the one on which I got up to 192. I think I could probably have got it up to 195 if I'd pushed myself that little bit more.
I went out today and attempted to discover my actual maximum heart rate. The highest rate recorded was 192 running up a hill. So this means that I can run at 150 - still feels slow but slightly more bearable than before!
Thanks so much for all your suggestions. I will go out tomorrow and try to discover my actual max heart rate. I did go for a run today and kept it below 146 as suggested by my hrm. It was still slow but not quite as bad. I'll see what the max is though.