When using the London underground - even in the rush hour, always get people offering me a seat. I always thank them for it and take it. I do have grey hair and use a walking stick and find standing very painful and difficult. Try not to travel in the rush hour, but sometimes it is necessary. London buses, again always get offered a seat.
If I am travelling anywhere by train I book a seat in advance so have no problems. Would not take the chance of long distance travel without a booked seat.
Also, at train stations where there are still steps, - if I am travelling with a suitcase, just stand at bottom (or top), and can usually have someone offer to carry up or down my case for me. Usually, these are quite young men or woman, some even going the wrong way on the stairs to help me.
I do not think manners have changed much over the years, however, I do notice how often people will accept an offered seat without even bothering to say Thank you. Personally, I have always found older people less likely to be helpful and courteous than younger ones.