one-way ticket vs round-trip flight

So my visa was approved (!!!) so I can fly into the UK now; however, one way tickets seem to cost a lot more than round-trip flights!  Is there any reason I can't just buy a roundtrip ticket and not use the return portion?  Have any of you done this?  tia!

Congrats on your visa!

Yes, I did it when I received my spousal visa and moved to the UK. In fact, I didn't even think about it because you are right that a one-way is always more expensive.

We also did the same thing for my husband when he received his US visa and moved back to the states. We bought two return tickets and never used the portion to fly back.

The other option is to book round-trip, return date being for holidays or visits.  That way it doesn't go to waste. 

That is what I did.  I booked the return for a few days before Thanksgiving.