Hey Enda,
Hope you are keeping well
I believe there is lots of choice for conversion these days, and all systems are all well capable as well.
You can convert to Graupner HOTT if you want to stay 100% Graupner. They do, or used to do a full conversion set + telemetry display if I remember. Then you use the Graupner Hott receivers etc.
Multiplex also do a module for 2.4ghz conversion.
Jeti also does a conversion with telemetry display (maybe not produced anymore, not sure!).
And if you want to do a bit of soldering, FRSky is still a very capable system if you can get a X module and the receivers (my first conversion was with my MC18)
Lot of options, it really depend of the overall cost of the receivers etc etc really, as the main issue I found, was not the conversion in itself, but more changing all my receivers
(I still have 2 radios as I transition everything slowly to a single system)