For England the Bowel Scope Screening Standard Operating Procedures are here.
https://www.gov.uk/government/publications/bowel-cancer-scre...
> Entonox pain relief should be available at all sites where bowel scope screening is provided, as the procedure will be performed without sedation, unless a decision was made and documented at a best interest meeting about the appropriateness of performing the test with reasonable adjustments.
Not necessarily, you can get the Good Stuff that knocks you out during the procedure in the UK (I have), but I'm not sure what the criteria are for getting it, if any.