Update requests from Tech Leadership Team

- Spend thresholds updated
- New point (19) added to code of practice 
*.service.gov.ukis intended for services, and "The service should not be accessible through search engines, nor should the URL be shared publicly." We shouldn't be linked to *anything* on service.gov.uk domains except from GOV.UK (and no, in my view the service manual does not count). We shouldn't make an exception here for ourselves as we would be unlikely to do the same for another department with a publishing site.