I think you still need line rental with someone for that option? Unless I’ve read it wrong which is definitely possible lol. They are a local company as well, so would consider supporting them.
I had assumed it was their SOGEA offering, but looking again, I think you may be right (although it doesn't definitively say you need line rental with another provider).
Another option is Freeola. £24.98 a month with silent line rental. You still have a phone line and can receive incoming calls, just not make outgoing calls. 30 day contracts for FTTC like IDNet.
I am an IDNet customer so not putting you off that option at all. I like the fact that they have a number of backhaul providers and will shift you to a different backhaul to try and resolve any problems. They have moved me from TTB to Zen and eventually BTw backhaul to resolve single thread speed test issues. In general their support has been exemplary when needed, however we did have three days of slow internet over the Easter weekend that they never found a cause for. I found some Sky customers on NextDoor who were having similar problems, so almost certainly it was down to an OR issue of some sort, however they were unable to shed any light on it.