Cheers all. Cougie, the RHR at 90 is a manual check, whilst the Garmin is reading 112.
Siggy, the consultant is sure that the procedure was successful (a few odd glitches but nothing sustained) so it doesn't need to be redone at the moment. But thanks anyway, you big old queen (I assume that's what you meant by Her Majesty"?)
It affects both the wrist one and the bike one, so I will go with the transmitter/belt as suggested.
I like the idea of contacting their tech department and will report back as to what they say.
I also tried emptying both devices, which can sometimes work but hasn't this time.
CD, are you mended now?
I am afraid I'm useless when it comes to things that don't have spinning shafts, Dusty.
What I would say from a technology POV is that you mention a wrist one? I presume you mean a Garmin watch picking up the HRM strap? Because it does raise the point that you could get a wrist based HRM - have a look at the MIO Alpha. Whilst it's probably a bit pricey for most, it uses technology licensed from Philips Medical to measure optically at your wrist. That's straight up geek points, but also may be more useful to yourself than most.