Yeah, we had it done a couple of years ago, not through Octopus (who I like a lot by the way) but through CB heating and got the BUS Scheme discount of about £5.5k.
We are very happy with it after initial installer failures, nothing to do with the tech.
Our personal contribution was about ~9k (so totally about ~14k) but we wanted to do it for environmental reasons as well as our boiler packing in.
The other point to consider is quite how much money you may save, as I know we have saved far more than I thought we would.