1. Register at LinkedIn, fill in your profile as much as you can (especially "skills" section) - it will start offering you matching opportunities. Also, you can find some recruiters there - they will be very happy to make you close the vacancies they're working on.
2. I believe UK also has some startup hubs, but I know only one in Oslo, Norway - and they have a page which lists all jobs in their member companies: https://jobs.startuplab.no/ - note that these are startups, so quite small companies, but I'm aware of at least one case when they helped relocating a non-EU citizen to Norway.