I picked up a new GoPro Hero in Argos for €129....they're back up to €139 now though.
It's not got a screen or wifi etc, but it's absolutely fine for 99% of users.

My mate has a Hero 4 Black edition with wifi, 4k and all the bells and whistles, but I couldn't tell the difference between them
when watching the footage back on the laptop.

I've used it a few times up in Ticknock on the mountain bike, works a treat.

The basic one doesn't come with any mounts, but I bought a few on ebay (handlebar/seatpost, helmet, car suction mount etc)