We describe a concatenative speech synthesiser for British English which uses the HADIFIX [8] inventory structure originally developed for German by Portele. An inventory of non-uniform units was investigated with the aim of improving segmental quality compared to diphones. A combination of soft (diphone) and hard concatenation was used, which allowed a dramatic reduction in inventory size. We also present a unit selection algorithm which selects an optimum sequence of units from this inventory for a given phoneme sequence. The work described is part of the concept-to-speech synthesiser for the language and speech project Verbmobil which is funded by the German Ministry of Science (BMBF).