There is a sliding scale of pensionable age depending on your date of birth. It is likely to be 62 for you, but do check the official source.
This may also be complicated by the fact that the bulk of your pension will be from UK source, so you may find that you will get some money from Malta at 62 and more from UK on reaching 65. As for how many years contributions would be required to get the minimum in Malta, I have no idea; this may again be complicated by years in UK.
I recommend talking this through with a professional before making any decisions.