An MSc is longer in the context it would take from starting university to achieve it. The MEng is 4 uni years of Study, an MSc is 3 uni years of study plus a calendar year of study.
An MEng is undergraduate, so it is roughly £3000 a year to undertake. An MSc is 3 years of £3000 a year (achieving your bachelors), followed by a year of postgraduate study, which tends to cost a bit more unless you can find sponsorship - rare at MSc level.
Although I appreciate the OP is in his 3rd year now so that point is pretty irrelevant.