Becoming British and keeping Dutch citizenship

Hi, I am a Dutch citizen and have permanent residence status in UK, and have lived in UK for nearly 35 years.
I am thinking of becoming a British citizen because of Brexit, but want to keep my Dutch nationality. I know that this can be done if I am married to a Brit. I have been in a committed long-term relationship with a British man for over 10 years, but we have never lived together and have no plans to do so.
Would our marriage be recognised as genuine (i.e., not one of convenience) if we married but stayed living apart?
Thanks!

As far as I know for BC there isn't a test of whether you are genuinely married - BC is not immigration law - you are either married or not. There are many cases where people live separated but still married. You will be asked the address where your partner lives but again this is not a hindrance. For BC purposes being married gives only one advantage, that of a shorter residency requirement (three years) but all other conditions have to be met irrespective of whether married or not.
I am not familiar with the rules around Dutch citizenship - do you mean that Dutch law allow you retaining Dutch nationality if married to a British citizen (or any other nationality)?

Thanks very much for your reply.
I am eligible to become a British citizen as a single person now, because my permanent residency is from more than 5 years ago. But if I do this I will have to give up my Dutch nationality, unfortunately.
The Dutch government does not allow dual nationality except under very limited circumstances - and so the only way I can have both is if I am already married to a British person at the time of AN application. There has been a petition to the Dutch government to get this changed, because it discriminates against single people, but they have so far refused.

Many Dutch people are now finding this out - a shock! Many other countries allow dual nationality...

Thanks again for replying

There are some married couples who live apart for long periods at a time, for one reason or another.

You may want to investigate all the legal implications of being married- taxation, financial support, inheritance, property, Social Security, insurance, etc.- would you consider getting married if possibly keeping your Dutch citizenship was not an issue.

Would such a marriage be considered as sufficient in Dutch law? No one on this forum is likely to know- ask the Dutch authorities or a Dutch immigration lawyer.