neoham

Plenty of contracting roles paying £500-600/day in London, a few even up to £800 (and 'Head of'/CTO level consulting gigs hovering around £1k/day although very rare as most of those positions are perm).

I know some rather mediocre developers on £550 day rates.

For perm positions, such roles aren't too uncommon for senior/lead level devs in finance, tech consultancy (doing SAP/Salesforce work at some place like Accenture, etc) or the top tech firms - though you'll want to avoid the underpaying Shoreditch start-ups.

Does mean living in London though, where a £100k salary still barely gets you a mortgage for a 3 bed semi. Plus, £100k will soon be worth about €27 but right now it's about 1:1.

They do, yes. Many public sector companies (inc HMRC) are now forcing contractors to be paid by PAYE even.

Generally though, you're safe as long as you work at the same company for less than 24 months. Then you need to find a new contract or relocate (working at a different physical office or taking on multiple clients can get around IR35 (if you fall within IR35 you're considered to be a disguised employee, not an independent contractor, and must pay higher income tax).

Senior/Lead UX designer at a big corp in London: making ~£115k/yr (~€130 at mythical exchange rates), salaried, before tax.

Actually took a pay cut, used to be a contractor with a day rate ranging from £600-750 which had me averaging approx £150k/yr and paying much less tax. Considering going back to that soon, although a bit worried about Brexit uncertainty, but right now I'm seeing plenty of contractor roles offering that much, a few up to £1k/day.