Not even worth bothering.
Those two jobs could not be more different, and if you think you're unlikely to see action as a HMO then you are very very wrong. They are Warfare Officers first, and weather specialists second. You could be sent anywhere in the world to kill or be killed. If you think the modern RN has no chance of going off and losing men, just look at the Falklands.
If you want to be a Para officer, start preparation yesterday. Everyone and their mum wants to be one before they go to sandhurst, and the truth is that only the very best make it each year. The competition for Officer roles in the Paras is ridiculous.