Again, i just did this both directions in about 30 minutes. Arriving on UA 930 at 6:30 I transfered to term 1/2 by bus (15 min) went through security (10 min) checked in at BMI (no wait) and went to gate for 7:55 depature. Noticed I was so early I went to bmi lounge. I had carry on only luggage - too heavy for bmi- but they didn't seem to care or notice. JUST make sure you DON'T go through passport control in LHR. It's VERY confusing and 2 different LHR staff told me to get into immigration lines, but you will do that in AMS. Have fun.