Miranda
You give your location as London. You should be able to find a good elocution teacher nearby. The teacher will also guide you on English phrases and expressions. Some classic English movies will give you a laugh and help as well, with actors like Alec Guinness, David Niven, David Attenborough and, the finest English voice of all, James Mason. The best ladies would be Julie Christie, Jenny Agutter, Jacqueline Bisset, Helen Mirren and, of course 'M,' Judi Dench.