Aquiss vs Cerberus vs File Sanctuary

My time with BT will be up in a few months and I have been looking around as to who to move to - when we got FTTP almost a few years ago BT where almost the only company we could go with as we were the lucky one's that benefitted from the Governments Rural Broadband scheme and overnight we went from 4Mbps ADSL to 1000Mbps...it was like Christmas came early

Whilst my time with BT has been good and we have had no issues and the speed has been great as a provider they constantly call you to trying to upsell stuff (despite being on the top package for broadband) and the recent in contract price rise and the charge for not returning old kit (despite advertising it as a free router, which I gave to a friend as theirs wasn't working) has made me think it's time to move but having done a lot of reading it's clear I need to be careful as not all providers are equal, I thought FTTP would be easy and you wouldn't have the old profile issues etc. I had in the ADSL days.

Having looked at some of the issues some of the providers have when on Zen backhaul I have got it down to a short list of Aquiss (which is reasonably local) , Cerberus and File Sanctuary (which I know the least about). We are a typical family where we use around 600GB a month (Hence why I ruled out A&A, although I would love to give them a go but costs are very high) speed is important but most of all we need the service to be robust as we cannot have lots of downtime (hence avoiding services with Zen backhaul).

Ideally we would like a service with fixed IP, high uptime, that just works, no traffic shaping etc. - can anyone recommend one above the other and if so why?

Additionally I am thinking of downgraded to a 500 Mbps service as 1000 Mbps seems to be a bit pointless as most services cannot deliver services at speeds anywhere near this, anyone else made that change? I am missing anything in my understanding here?