Yep. Even being heavily pregnant, if a really elderly person (or disabled) gets on and nobody else can move (say, if all the other priority seats are taken with similar people) I'll offer. If people are sitting in the priority seating who don't have priority though, I'll say, "Excuse me, this lady (or whoever) needs to sit down." Similarly, if I get on and nobody offers me a seat, and those priority seats are not filled with elderly, disabled, pregnant or prams, I'll ask people to move of nobody offers. People are damn rude, and I've found rarely offer. I have no issue in asking people to move. Especially young people, or obese. Sorry, those seats are not for you.

I have to say though, depending on the person (how they look etc) I wouldn't necessarily offer my seat to someone on their 60's, definitely not pregnant anyway. If they look an old and frail or weak 60, then yes I would, but I know a lot of people who are 50-60 who are good to stand. Obviously later 60's is different. I guess it comes down to a bit of respect, and a bit of circumstance too.