It may be a bit late in the season but it's worth trying in the greenhouse. Ideally, plant the melon in the bed in a slight mound of rich compost, as the stem can rot if it gets too damp. Otherwise a large pot should be ok.
Allow the leader, the main stem you can see in the centre of the picture, to grow to about four feet long, and then pinch it out. This will encourage sideshoots to form.
Wait until there are both male and female flowers on the stems at the same time. The female flowers are the ones with the tiny fruitlets already at the back of the flower. Then pollinate the flowers around midday by taking a male flower, removing the petals, and pressing the anthers into the stigma of the female ones. If there are plenty of pollinating insects around anyway, you shouldn't need to do this.
With luck you can get three or four melons set together. Once the fruit has set, keep any new shoots pinched back. Then it's just a case of watering well as they grow. Withdraw watering as the melons approach ripeness to get the best sweet flavour.
Good luck. Let's hope we have a nice warm Indian summer so your melons ripen well.

Thanks very much Bertie

Yes, you may still get some fruits. following Bertie's (as always) wonderful advice. All the Best, Peter!