I am thinking of getting the above HRM to help me with my training. At som,e stage I may invest in the power meter attachment. Does anybody know if the Power information is downloaded along with cadence and other information?

I believe so. You won't go wrong with a 710. Very reliable.

"polar 720 inc speed and the cadence is only 30 extra, total cost 210 if you shop around, its good on a road bike but tried it on my ht which has 100mm z1's and the trnasmitter for speed was not strong enough! even with sag and the magnet as high up spokes as it was possible so that is a limiting factor!"

power is downloaded at same time