How is it not shifting "quite right"?Slipping gears,missing gears....?
I think you'd be better off getting it going as a 3speed.You'll be able to get more $ for it.The fixie crowd like their bikes 531 or better so a steel Raleigh might not be what their looking for.But there IS a resurging interest for the old Raleigh 3speeds.
As you can tell by my title,I like Raleighs.Maybe I'm a little biased but when you have one of that vintage and it has most of the original parts it would be a shame to start modifying it now.It's almost 50 years old.You may just have to clean and relube the hub to get it working properly.