First of all try not to worry, most visits to the breast clinic end up with everything being fine.
Your husband can definitely attend, but they are usually left in the waiting room when you have to actually see people.
I have had two visits and both have been identical. They went like this -
Arrive.
Sit in waiting room.
Get called through to get changed into an easy access gown, clothes go in a basket that you cart round with you/leave with oh.
Back to waiting room.
See a consultant who will chat through what's been going on, give you a manual examination and explain the rest of the visit.
Then ultrasound, cold gel, otherwise entirely uneventful.
Back to waiting room.
Then mammogram, not going to lie, for me, feckin painful, but super quick, so very tolerable.
Back to waiting room.
Back to consultant who will review what if anything has shown up.
Visits were for me about 3 hours ish.
There is a lot of waiting about.
I hope that helps somewhat and that everything turns out to be fine.
Also your user name is awesome, and my dd's nickname 