Upvote:5
They will look and see that you are arriving from Schengen and departing to Schengen. This will disqualify you as a bona fide transit case and then it becomes a matter of luck: they will either refuse or reject your application.
If they reject your application, they will refund your fee and probably call you with a brief explanation that you do not qualify. If they refuse, matters will be worse.
Convoluting your itinerary to obtain more frequent flyer miles is a great idea as long as you leave the UK out of the picture. You can try transiting through, for example, Rabat or Gomel and it might pay off.