IDNet did swap customers from ZenW to TTB if there were problems, but this stopped being an option a few years ago, around the same time that Zen stopped doing it for their own customers. So IDNet are pretty much tied to Zen and are probably using Zen's wholesale service to get their customers data into their kit.
Uno were always brilliant when I was with them for a number of years, unfortunately they still don't do IPv6 which is now a requirement for me to get to some work machines when working from home. When I checked pricing for FTTP 1000/100, they were quite expensive, matching AAs pricing.
I went to Aquiss after IDNet and had problems from day one. I had really bad congestion at certain times of day, we are talking 900Meg dropping to 8 or 10 Meg on the worst days and huge increases in latency!
Worth noting that Aquiss aren't an ISP, they are reseller, they resell Entanet's product (Entanet now owned by CityFibre). So Aquiss can't buy new kit, add capacity, reboot switches etc, it all goes via CityFibre Wholesale. After months of back and forth CityFibre said they could find no issue or problems with congestion and Aquiss let me leave the contract early. A few months after I left, Aquiss/CityFibre had problems with their network and invoked their 'emergency' network teams, apparently they had run out of capacity and everyone was grinding to a halt. I can't believe they didn't know they were running their network hot, people like me had been suggesting capacity problems for months and just told to go away essentially.
So I bit the bullet and paid a premium for AA, went live, all my kit was exactly the same as it was with Aquiss, just updated the username and password and all congestion issues vanished instantly. Aquiss had been suggesting my problems were local to me and likely related to capacity issues in my area, i.e. a BT Wholesale issue, but that was proved completely false as I was still going via BT Wholesale with AA.
As for AA, just can't fault them, over a year now and its been reliable with no slow downs. Think I've had one issue where I got thrown offline during the day as they had a problem with a router. As their service status gets updated immediately (not hours after the event like most), I could see it wasn't my end so saved all the rebooting of kit to rule me out, so I went for cup of tea, and by the time I was back it was up and running again.
Good luck with who you decide to move to next.