By Alistair Smout LYDD, England (Reuters) -Britain is stepping up its support for Ukrainian soldiers through the winter, Defence Secretary Ben Wallace told Reuters on Wednesday, following weeks of Ukrainian advances towards the southern city of Kherson. Wallace joined NATO Secretary General Jens Stoltenberg to observe the training of Ukrainian troops in the southeast English town of Lydd, as Britain announced the delivery of a further 12,000 extreme cold-weather sleeping kits for Ukraine. “Winter is approaching and that is an important challenge for both sides,” Wallace said. “So we’re determi…