When does your midwife /doc perform a sweep?

Emma
I am just wondering when others are going to have a membrane sweep? My midwife has me booked in for one which is optional at 40weeks + 4...but from reading others experiences on glow some people seem to have them as early as 36 weeks. 
 (I live in Scotland, UK, so maybe 40+ weeks is normal?)
When do you get the option to be induced in your country? Thanks