Train from Frankfurt Airport to Luxembourg

The best place to find train schedule information is on the German Rail (Bahn) website. Use "Frankfurt(M)Flughafen Fernbahnhof" for 'from'. I would assume you will want to use express trains from the Fernbahnhof at the airport to Luxembourg. I see five connections between 6:30 and 9:00. The fastest connections take about 4 hours. There are two stations at the airport. The Fernbahnhof services the faster express trains. It is near Terminal 1. You get to it by going up to the 2nd floor mezzanine of the Arrivals Hall and taking the pedestrian bridge to the building across the access road from the terminal building. Follow the hallway (and signs) out through the building to the station. It generally takes me less than an hour from landing until I am waiting for my train at the Fernbahnhof. Depending on the time of day, it might be just as fast to take an all regional connection. If you choose to take regional trains, there is the closer Regionalbahnhof. It's under the building across the street from Terminal 1 and you get to it from inside the terminal; go down steps next to the outside wall and through the mall under the street. In your case, I wouldn't look for an advance purchase, discounted Saving Fare tickets. Those tickets are train specific, and if your flight were late, the tickets would be worthless.

Thanks for your info.
Do you think it would be easier and quicker to fly to Paris and catch the express train from there to Luxembourg. I am really confused which would be the better option.

Here's a thought...have you looked into flying from JNB to Luxembourg? You'll have to change planes along the route but it may be the most convenient.

I did consider that but the thing is that we are travelling on to the UK after our visit to Luxembourg and so it will effect our return flight to Johannesburg. The trip to Luxembourg is basically a bubble in our ultimate trip to the UK.

Have you tried using multi-city booking for your tickets? JNB-LUX and then LHR-JNB? And there are cheap flights on British Airways between Luxembourg and London. I know because I'm in the process of booking this route.