I had to have a sweep. Didn't find it at all painful, just a bit embarrasing (if you know what they do), plus I didn't entirely love the midwife doing it!
It didn't work at all and had to go into hospital and be induced. This turned out to be much better than I was expecting (had scared myself with all the horror stories) and my son was finally born perfectly fine nearly 2 weeks overdue. And all just on paracetamol and gas and air!
I had a sweep on boy 1 - it didn't hurt but it is definitely not on my top 10 list of fun things to do. I was already two weeks over so it may or may not have helped.
i had a sweep at 41 weeks with first (youre being offered early) and it did nothing at all.
i had a sweep at 40 weeks with second (had a check up at hospital due to gestational diabetes and a consultant did it, he was very rough but thorough). i then had plug and blood traces for 2 days and it stopped for 24 hours before baby arrived at 42+4. No idea if it was the sweep that helped or not.
Dont forget a sweep will only help if baby is in the right position in the first place.