Upgrade Garmin heart rate monitor

I have a  garmin forerunner 305 with old style hr monitor (hard strap) but i feel i always get a high heart rate reading. It is not uncommon for my heart rate to be at 90-100 before starting run and quickly rise to 180+. I don't feel i am working hard enough for a 180+ reading. So I looked up on google and saw all the usual things like wetting sensors and tightening strap which i have tried.

But then I came across an article in which someone had same problem so he used a polar strap with his garmin sensor as with the premium garmin straps the sensor can be taken off and swapped on to a polar strap and the guy claimed he got better readings. Anyone any experience of this?

Either difference between garmins old (hard) strap and new (soft) strap.

or Using garmin sensor on polar strap?

Had the Garmin soft strap for about a year. I got the occasional spike at the start of a run, but everything then settled down. Over the course of the year the strap became more unreliable, with spikes throughout runs. I recently bought the polar soft strap for ??10, and with the Garmin sensor attached its been perfect. I'm not too impressed that Garmin expect you to replace the strap and sensor at a cost of ??45

I also have the Garmin hard strap that I use for rowing. I find it really reliable, although not quite as comfortable for running. Its important with the soft straps to wash them after each use otherwise it seems to shorten their life.