Yeah you would need to get an SEP rating and possibly a type rating for specific (complex) singles. Most flying schools can provide this. Pretty sucky that we get this far, have a license that let's us fly a complex multi in crappy weather yet we can't take a 152 up in beautiful weather.
I remember my flying instructor telling me that if a PPL turned up to rent a plane from him he would be pretty confident about it, but if an ATPL holder with 2500 hours of jet time turned up to hire a plane he would be very worried!