Cat Driver is correct it is all about risk assessment. What are the chances of an engine failure flying across the channel? Who knows but it would be prudent to be prepared in case that should happen. Fly the shortest route possible. Fly as high as possible/allowed. Have the equipment needed to spend time in the water/mountains to be alive when SAR get to you. Having 2/4 engines is great but we have to operate with one. Therefore we must weigh up the risks and decide if we go or not. I do fly single engine IFR and at night. The planning is more involved and get outs are thought out more carefully. Prepare well and have fun.