... I'll never marry

This is NOT a comment on your decision, but in most countries, and certainly in the UK, 'marriage' is a mixture of two entirely different things. One is the social/religous aspect, with its historically unbalanced relationship between the male and female partners. By and large it is this people object to. But, and importantly, there is the relationship between the partners and the law, and there a huge number of things like pension and inheritance rights that do not apply unless you are married. So anyone who chooses not to marry would be well advised to spend a lot or time (and money) with a good lawyer making sure all of this is sorted. It needs to said again and again that currently living as partners does not bestow any legal rights (UK) to, for example, inheritance. It is reviewed occasionally but I believe the situation has not changed recently.