What I found was that the calories burned on MFP were only close to accurate (according to HRM) when I first started spinning, but the gap steadily widened as I got fitter and presumably more efficient. I do think my HRM is roughly right, because when I was carefully sticking to the calories I was allowed on MFP using the HRM as a guide for calories burned through exercise (so generally eating most of my exercise calories), I did lose 7kg.
I had six weeks off the spinning & cycling after the wisdom tooth op went a bit wrong (increased heart rate isn’t somewhere you want to go when you have a throbbing dry socket in your mouth) and then it was Xmas. I’m almost back to the calorie estimates of MFP being the same as my HRM again.
I am now at the weight I want to be, I ‘just’ need to maintain it. Myself and Rob are now on a bit of an austerity drive for various reasons, which involves much cooking from scratch and taking lunches into work, which will help a lot. Really I just need to curb my talent for making enormous amounts of chocolate disappear, which has started up again over Xmas and not wanting to go away.