Immobilise is what I use, and not just for bikes.
It’s free and if you are happy with recording your frame number then you don’t even need to buy the datatag thing
Same here – it’s linked to the police national property register and it is what our local force register you with when they do bike marking days etc (so hopefully they actually use it).
I’ve uploaded my bike details plus a few good clear pics showing the full bike, close ups of the frame number and identifying features etc.
No bothered with a tag thing though – I think if they go to the effort of filing off a frame number then they’ll also look for datatags.