The actual record (as in the original parish record) certainly does not say IoM England nor I doubt would it read mylbrea - in the first case the IoM & England bit was added by the Mormons when they constructed the IGI, I believe the England was added as they were under the mistaken belief that the Island was a county of England. For Mylbrea - this along with many other 'strange' names are usually a misreading of the official transcription of the parish registers (as this was done in 1911 the handwriting is generally quite clear but I believe the Manx records were one of the first data sets to be handled by the Mormons and their volunteers had no experience in Manx names (typical misreads are kemish for kinnish, kipag for kissag (long 's' misread as 'p'), 'm's and 'r n's often confused, 'o's, 'a's are often confused as are 'e's and 'i's). In a few cases (very few in my own experience of comparing the original regs + the 1911 transcription) the 1911 transcriber made a mistake (usually in non-Manx names) but sometimes the original register is very untidy, the writing poor or badly worn (especially at page margins).

Obviously you can enter whatever you want in your own records but I suspect you may then find it difficult to verify any ancestral trail.