Please hold the line, a rival operator will be with you shortly. Vittorio Colao, Vodafone chief executive, can expect a fight if he makes an offer for T-Mobile UK, the country’s fourth-ranked mobile phone group. It did not take long after news of Vodafone’s interest in its struggling rival broke on Monday to hear that Telefónica’s O2 and France Telecom’s Orange were looking at possible combinations, too. The prize: big cost savings and a dominant position in one of Europe’s most competitive telecoms markets.