A little update:
First sensor on stomach fell off after 4 days. I do have too much stomach and cant inject there as it hurts too much so maybe it isnt a good site for me, or maybe its because my stomach is too round! I won't use it again.
Second sensor on left thigh lasted 3 weeks 3 days i think, then stopped working. I used this with the official receiver which meant i restarted the sensor every week.
Third sensor on right thigh lasted 5 weeks 3 days, still working fine other than the odd reading out of line, but then i knocked it off whilst undressing. I used the xdrip only with this as i had returned the borrowed reader. No restarting of the sensor required, it just works till you stop using it.
I've now inserted a fourth sensor which i have put on my left thigh. Hoping it will last a few weeks