Many AM only radios can have a VHF tuner added to them. This obviously allows you to receive stations on the standard FM broadcast band. There are various options available depending on the specific requirements of your radio. Pricing varies depending on the complexity of the addition but is typically in the range of £60 - £120.
Most vintage radios can have Bluetooth added to them, which allows you to stream audio from modern sources such as your smartphone. Typical cost is around £40.
Many valve radios can be modified to receive DAB/DAB+ stations. This premium upgrade is a custom made unit which replaces one valve in your set with a German engineered module. The rest of the set remains original. Stations are tuned as before using the standard dial on your radio. Typical cost, £175.