The first Trix locomotive sold in the UK for Xmas 1935 was in a box with 3 coaches, a circle of track and a controller. Introduced by Bassett-Lowke it was referred to as the Twin Train set.
Although the loco tender has the words 'Trix Express', a close examination shows it is an over paint with the word 'Twin' underneath the word 'Trix'. This would be more in line with the catalogue. Throughout the text in the catalogue it is referred to as the 'Twin Train'. Nowhere does the word 'Trix' appear in this first catalogue, even the photo of the engine has the words 'Twin Train' on the tender. It seems a last minute decision was taken to use the German name 'Trix' on the loco.
At about the same time as Trix introduced DC for the three rail system, Trix Express in Nuremberg started in 1953 to produce a 4.5 - 6 Volt motor for a simple battery train. One of the major aims of Trix, was to reach children and juveniles of the fifties with an easy to handle and low-priced train set, in the hope they would be won as future customers for their main DC system. In cooperation with the toy manufacturer Distler, who had developed the famous Distler Motor, Trix Express produced several variations of battery trains up to 1960 (e.g. the 'Dieselzug' TE 7/900 and the 'Sandbahn' TE /601).
See also this Wikipedia article on Trix Express.