Limited or almost no experience with MGTF engines but I agree with the use of flushing oil first. That worked a miracle on a Vauxhall engine with noisy tappets. It also cleaned out a small Peugeot engine system for us soon after buying a 106 for daughter’s first car.
I’d try that first Len, drain it out whilst hot and re fill with oil of your choice after a filter change.

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