Hi Milly and welcome to the vine.
My first year at melons but if the fruit is still quite small there's every chance that the male flowers will be along in time. I have just "interfered" with mine and, using a paintbrush, just brushed the inside of the male flower then the female with the pollen laden brush.
I should think that if you have them in a greenhouse you will certainly need to hand pollenate or put the plant outside on sunny days for the bees to do their thing.
Fingers crossed for both of us
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