I'm based in Europe and I have mostly worked in EU countries, except for a couple of very lucrative contracts in the Middle East. I can see you are based in London: London has tons of contract gigs, especially in the financial sector (mostly using JVM languages I'm afraid). If you can move around, Switzerland has also lots of contract work at the moment - and low taxes.
Take a look at jobserve.com for UK contracts.
What has worked for me so far:
- Find some good recruiters from reputable hiring agencies. Once you establish a relationship with them, they can provide a stream of constant contract opportunities. You can accept or refuse, based on location, rate, tech stack etc.
Unfortunately, this is easier said than done, because the bar for entering an hiring agency is quite low these days and you get all sort of cowboys. Personally, I prefer to work with older dudes with at least 10 years of experience in the fields (reverse ageism!).
- Never, ever leave a company slamming the door. If you do a good job, they will call you back
- Linkedin lists contract gigs sometime, I have never really got anything out of it, but it's good to keep an eye
- At some point, I wrote a book that landed me a couple of good gigs. I'm not suggesting to write a book, but you can try to establish yourself as an authority is some field (Elixir, Rust, etc). Again, easier said than done
Ultimately, the hiring agencies are the gateways to the majority of contract gigs, so you really want to talk to them.
Good luck!