I have just had the same situation a couple of months ago.
I got offered to move from Southampton to Plymouth for a promotion. I'm 23 and it's a bloody good promotion. I had a great life in Southampton. Great gf, great group of mates, easy living really.
I took the job, I travel the 3.5 hours back to Southampton on Friday afternoons, and go back to Plymouth in the early hours on Monday. I don't regret it at all. It gets hard sometimes without the missus, but it's not like we have kids or anything and if we're meant to be, it will work.
So from my experience, take the job.