HRM recommendations from UK users (and US) needed!

Hello all,

I'm just entering week 7 of Insanity. I've made changes to my diet and its going well so far but one thing I really want is a HRM. In terms of requirements I'm looking to spend no more than £50 if possible (the cheaper the better). I want to be able to press a button at the start of my workout and then another at the end and it calculate how many calories I just burned.

Has anyone got some good recommendations? I know there's loads of higher end bands available but I don't know if I'm prepared to spend £100~ on something like that. Any advice much appreciated :)!

Thanks