Hi Darragh,
Yeah, I swapped over to a polar strap for three reasons.
1. I was starting to get some dropouts in signal which were down to the strap becoming dodgy over time
2. The Garmin strap kept coming loose as I was running/cycling which was a pain
3. My skin doesn’t agree so well with the Garmin straps so I was looking for an alternative
I use this one
http://www.amazon.co.uk/dp/B00JWVEQLC/ref=twister_B00893LQNK
in the xs-s size which fits me perfectly. They’re a damn sight cheaper than the garmin ones and you can find them at a really low price if you shop around online.
Cheers,
A