simonp, I would loved to have had a power meter on my training bike when I used to race, all that lovely data. However the fundamentals of training don't change, what are you trying to achieve with the intervals. Intervals are supposed to allow you to work at a load that you can't sustain for a longer period which will normally be above your AT or AKA FTP. They are normally done after a solid foundation of lower intensity higher volume training.They are supposed to put the icing on the cake. Training at a specific level is improving a specific physiological function, this hasn't changed just the ability to see the exact workload not one derived from heart rate or perception. If I had a power meter I would use it to train using the well established and proven Peter Keen zones method where the power meter would be used to maintain a constant output over varying terrain without the delay a hrm gives to changing work load. Working at your FTP is hard work, I would try to plan those sessions into something like a club 10 or 25 where the competition is more of an incentive. Sorry I cant be more help, I can't read the figures on your sheets but I would suggest that you need to first establish what you want from your training, then develop a plan, then stick to it for 6-8 weeks and see if you are getting the results you want. I used to have a undulating little loop just under six miles and would time myself around it and over time the laps got quicker.