If you've been invited and are hesitating about what it might be like, here's my take:
I got the invitation by letter a couple of weeks ago. The local centre is female-staffed and you go in, give name and address, then go into changing room, remove bra and put top back on, then back to waiting area. I was second, contemplating how weird that feels.
Then into examination room.
Mammographer takes details again, asks a few questions, then off we go.
Top off, otherwise fully dressed, stand in front of The Machine. It's a big thing, but the relevant bit is all you'll interact with. It's a unit attached to the front which she then raises or lowers according to your height.
You then lean in, she'll give you guidance on where to shuffle feet, turn and lean for best position. Your right arm is draped along the edge, fingers in the notch and she may manipulate your right boob into place so it sits nice and flat on the shelf. Your armpit is part of the exam so she may get in there too.
Then the plastic cover moves down and compresses your breast against the shelf for a few moments while the image is taken. Then it moves back up.
Then you twizzle round and do the other one, then again at another angle. Done!
Does it hurt? For me, not one bit - tho I did take 2 paracetamol an hour before, just in case. If you have had frozen shoulder or a back issue as I have had, or arthritis or anything where standing at an angle and holding position might tweak, it's worth bearing in mind for that. But for the actual boob compression it was absolutely painless.
I was in maybe 8 minutes though when I came out there were six waiting.
I should get a letter with results in two weeks.
Would you like to know anything else?