… that some European countries and regions still bear Celtic names?
In the case of Ireland (Éire), Scotland (Alba), the Isle of Man, Wales (Cymru), Cornwall (Kernow) and Brittany this seems self-evident.
But Belgium (La Belgique, België) and probably Portugal are also named after Celtic peoples (Belgae, Callaeci). In addition, we find Galicia, Helvetia as a symbol of Switzerland and the country’s name in Irish (An Eilvéis), Greek (Ελβετία) and Romanian (Elveţia).
The name of the Celtic Volcae is the basis of German welsch ‘Roman, foreign’ and English Wales, but also of the Lithuanian and Latvian names for Germany (Vokietija, Vācija) and even the Polish name of Italy (Włochy).
Bavaria and Bohemia ultimately owe their name to the Celtic people of the Boii (Baiovarii, Boiohaemum).
… that the two-wheeled Celtic chariots had shock absorbers already in the fifth century BC?
We know such chariots from tombs in southern Germany, the Middle Rhine and Moselle rivers as well as the Champagne and Yorkshire. After the reconstruction of A. Furger-Gunthi and most recently by D. Stifter and R. Karl the frame was not firmly mounted on top of the axle. Rather, the frame bearing the seat and the other superstructures rested on ropes or belts which were stretched between the drawbar and the V-shaped shafts directed to the rear. Thus unevenness of the terrain could be cushioned.
... that the Celts were among the first Europeans, after the Greeks, to use the alphabet?
The Greek alphabet of Euboea had already been adopted by the Etruscans around 700 BC (Marsiliana tablet) and was handed down to many neighbours such as the Venetians, Oscans, Umbrians, Faliscans, Romans, Messapians and various Celtic peoples. A graffito from Montmorot in the Jura Mountains in France from the time around 600 BC and Lepontic inscriptions from the beginning of the sixth century BC are some of the earliest attestations; see http://www.univie.ac.at/lexlep/wiki/JU·1 and http://www.univie.ac.at/lexlep/wiki/NO·1_Castelletto_sopra_Ticino .