GP 2ww referral to breast clini

Hi, I've been referred to the breast clinic for a scan and was hoping for a little info. I found a ridge/lump a while back in my right breast. The other side has the ridge too but this side has definitely got bigger over the last few months. I have lumpy breasts anyway, I think they feel pebbly, if you get what I mean. The gp had a feel and said that too but then she said that there was a big pebble but it was highly likely it was nothing sinister. I have my appointment at the clinic on Monday. What happens there? Would they examine me and if they think it's nothing to worry about, will they not do a scan or would they do it anyway to be 100% sure?

Thanks in advance xx