I spent 8yrs working as a contractor in London for rates between £600 - £950pd.

Architecture roles - which to some companies meant spending time coding (yay) and to other companies spending time on non-coding activities; aligning teams, strategy, planning, managing stakeholders, slide decks etc...

Cloud/Security Operations usually hit 600-1k. Higher end of this would be government contractors that need to pass through stringent/strict security clearance ie. UK nationals etc. Even some non-gov contracts want SC sponsorship because end client will usually have sensitive customer data.

You can see market trends by looking at reports published on the top 5 UK IT recruitment websites (usually published every 6 months), ITJobServ is a good site too for real time trends.

London based contractor here. It's sort of hard to say since rates keep going up. My gut feeling is 700 outside/850 inside would put you in the top 10%.

I've had a few short-term contracts (3 months or less) at £950-1100/day as a staff level data scientist, although those are usually 'exceptional need' situations where the company has their back against a wall for some reason or another.

These days it feels like the market is actually cooling down to me, but that could just be because I'm looking in the wrong sectors.