tbh, at 18stone, unless you're 7 foot tall, i doubt you need to be taking eph to lose fat.

Just go past the comfort zone with the cardio, 2 hours a day if you want. Drop the cals to 500 sub maintainence, so circa 2000/2200 a day. High in protein, moderate in fats and low on carbs with one high carb day a week.

Give it a couple of months at that and i'd put money on you being down 2stone+ if you are banging in the cardio at 90mins+ 7 days a week.

If you do go for eph, at 18stone... got to be looking at 100mg a day of eph, split over 3doses with 200mg caff a dose aswell as 1 asprin.