@Kimbaland
YANBU to not want to give anything; that is your right.
YABU to expect anything from work colleagues for your engagement.
I certainly would not be giving anyone at work anything for getting engaged.
If it's a milestone birthday, I wouldn't have a problem chucking 2 or 3 quid in. (21, 40, or 50, or 60,) but any other one I wouldn't be contributing.
I used to work in an office block with some 35 workers, and there was ALWAYS bloody something... A birthday, a new baby, someone leaving, a milestone wedding anniversary, a milestone birthday, etc etc, and it seemed like I was forking out every sodding week.
I have a friend whose two young adult DD and DS, didn't even get them a card for her and her DH's silver wedding anniversary. In fact, the only card and gifts they got was from each other. This was 3 years ago, and she is still wounded about it. I mean, I see her point, her adult DC could have got a card. It was their parents silver wedding anniversary. So I think she had a right to be upset.
But to expect stuff off work colleagues for getting engaged is a bit mad to be honest. Unless you are throwing a party for it, no-one is going give you anything, and you shouldn't expect it.