Hi, 27th formed 1689 was later 1st Battalion, Royal Inniskilling Fusiliers. I see you have Irish family connections which makes sense, although even English regiments could have 25 percent Irish personnel. They had better terms of service. The wife could draw part of his pay at home.
A lot of men were let go in 1814 although your antecedent left through illness. The remainder were sent to America to, amongst other things, burn the White House down, cough. This caused problems like a lot of 2nd Battalions had to be used at Waterloo.
Unfortunately, I no longer have my Napoleonic Wars OOB's. It's possible that the 27th was in in the Peninsular. There was a medal for that. I'm afraid I don't know what 33/12 means.
Roger