Do i need a gp referral for a gastroscopy or colonoscopy? i'm pretty sure i'll get referral for one, so i just want to skip the whole gp process

Not sure: I am not sure in your country but usually you will need a referral in the US.The reason is they want someone to send the results and coordinate the care if abnormal.Usually they also want to know if the referral is appropriate and some basic labs beforehand.

Insurance issue: Some insurance requires it. Some do not. If not required by insurance you can usually omit the GP.