Hi
I flew from Blackbushe to Barcelona earlier this year. If you have a flyer magazine from a couple of months ago then there is a write up in there.
I planned a direct route from Cherbourg to Barcelona straight over the top at 12000'. The highest point around there was just over 10000' As has been said there are not many options in the case of an engine failure but we were in a Cirrus so always had the chute as a backup. I really didnt know for definate whether we would get the cloud base to get over safely, so I planned Perpingnan as an alternate and would fly there then route around the coast if we needed to. This may be an option.
The flight actually went really well and we got straight over no problems. Once the ground starts to fall away at the other side it is quite a steep decent though into Sabadell. On the way back with full fuel and hot weather it took a bit of climbing to get up to the required altitude.