I've got a separate SIM - works well, as less likely to be found than another phone and easier to keep on me. Of course, you then need your personal phone to be easy to swap SIM cards in and out of (ie not an iPhone). I think using a different number just keeps it simple for me....
i phones are a bit lethal, even with a second sim. In my case, I have an ipad, which is linked to my main phone and sim, through i Cloud. Swop sims and the ipad starts asking all kinds of questions eg do you want to link this number for FaceTime blah blah.,,
OH uses the ipad, guess the rest..
Some may say a solution is to turn off all mobile data, wi fi, in fact anything that can cause the iPhone/ipad to link. Going into Starbucks nearly had me once, as the second sim connected to the wi fi. When I got home, there were the usual questions on the ipad regarding the " new user phone number " Got away with it, before the OH was home..
My advice, get a very cheap non smartphone and hide it, or have an excuse, as detailed in the many threads here..
ps as an aside, in my stupid pre- UKP days, I used my own iPhone. Last week, a WG connects with me on Linked In, four years after last seeing her! Running some new make up business etc. Email in my Inbox, suggesting we connect, also invite on Linked In. Which is on the ipad too.
I was away for a week on business, ipad at home with the OH. Got away with it again, didn't clock it...Linked In now deleted from the ipad..
A fucking risky game this punting lark, just when you think you've covered all bases